WO2023193369A1 - Lithium difluoro(oxalato)borate doped and coated sio/c composite material, preparation method therefor, and application thereof - Google Patents

Lithium difluoro(oxalato)borate doped and coated sio/c composite material, preparation method therefor, and application thereof Download PDF

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WO2023193369A1
WO2023193369A1 PCT/CN2022/106926 CN2022106926W WO2023193369A1 WO 2023193369 A1 WO2023193369 A1 WO 2023193369A1 CN 2022106926 W CN2022106926 W CN 2022106926W WO 2023193369 A1 WO2023193369 A1 WO 2023193369A1
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lithium
sio
composite material
doped
coated sio
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French (fr)
Chinese (zh)
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易旭
廖寄乔
戴朝晖
卢治斌
曾鹏
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湖南金硅科技有限公司
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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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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 invention relates to a lithium ion battery negative electrode material; in particular, it relates to a lithium difluoroxaloborate doped SiO/C composite negative electrode material, and also relates to a preparation method and use of a lithium difluoroxaloborate doped SiO/C composite material.
  • the application of lithium-ion battery negative electrode materials belongs to the field of lithium battery technology.
  • Silicon is the currently known lithium-ion battery anode material with the highest specific capacity (4200mAh), but its huge volume effect (>300%) will lead to a sharp deterioration in electrochemical performance. Therefore, silicon oxides with smaller volume effects have become an ideal choice. Among them, silicon oxide (SiO) has a small volume effect (150%) and a high theoretical capacity (>1500mAh). It has become a hot topic in the research of negative electrode materials for lithium-ion batteries in recent years.
  • Chinese patent (publication number CN109524621A) provides an electrochemical pre-lithium technology. It assembles a half-battery model by prefabricating silicon-oxygen material negative electrode sheets and metal lithium sheets, and performs pre-lithiumization through external discharge of the battery. Pre-lithium The first-week efficiency of the treated silicone material can reach more than 90%.
  • Chinese patent (publication number CN112151771A) provides a silicon-based negative electrode material with a silicate skeleton. It mainly incorporates a silicate skeleton of Mg and Li into the SiO material to improve the expansion and stress of the silicon-based negative electrode to achieve improvement. The purpose of material recycling performance.
  • the SiO material itself expands and contracts, causing the material to pulverize and collapse, and the current collector is peeled off, causing battery failure. Its expansion will also cause the SEI film formed on the negative electrode to be extremely unstable. Constant rupture and reorganization consumes a large amount of active lithium, which reduces the Coulombic efficiency and cycle life of the battery.
  • the first object of the present invention is to provide a lithium difluoroxaloborate-doped SiO/C composite material (SiO/C@LiODFB), which is composed of lithium difluoroxaloborate. It is deposited and uniformly coated on the surface of SiO/C particles.
  • the carbon coating layer can effectively improve the conductivity of the silicon oxide material and provide a buffer for the expansion process of the SiO material, and lithium difluoroxalate borate can form on the surface of the negative electrode.
  • the stable and dense SEI film is not easy to break, and can continuously and effectively slow down the consumption of lithium source by the SEI film, while reducing the formation of lithium dendrites, increasing the service life of battery materials and the high and low temperature performance of the battery.
  • the second object of the present invention is to provide a preparation method of lithium difluoroxaloborate-doped SiO/C composite material, which is simple to operate, low in cost, and suitable for large-scale production.
  • the third object of the present invention is to provide a lithium difluoroxaloborate-doped SiO/C composite material as an anode material for lithium ion batteries. Its application in lithium ion batteries can effectively improve the Coulombic efficiency of lithium ion batteries. and cycle performance.
  • the present invention provides a method for preparing a lithium difluoroxalate borate doped and coated SiO/C composite material, which method includes the following steps:
  • the technical solution of the present invention first uses SiO material as the core, and coats the outer surface of the SiO material with a uniform carbon layer through the CVD method.
  • This uniform carbon coating layer can not only effectively increase the conductivity of the SiO material, but also can reduce the expansion of the SiO material. Buffering is provided during the process.
  • lithium difluoroxaloborate which is conducive to uniform and in-situ doping and coating of lithium difluoroxaloborate outside the carbon layer, while SiO/C
  • the surface-coated lithium difluoroxalate borate can form a stable and dense SEI film on the surface of the negative electrode during the operation of the lithium battery, which can effectively reduce the rupture and reorganization frequency of the SEI film, reduce the consumption of active lithium, and greatly increase the Coulomb density of the material. efficiency and cycle life.
  • the particle size D50 of the SiO powder is 3 ⁇ 8 ⁇ m.
  • the conditions for the CVD vapor deposition are: gas carbon source flow rate is 0.5 ⁇ 5 L/min, temperature is 600 ⁇ 950°C, time is 0.5 ⁇ 5h. Under optimal conditions, it is beneficial to generate a uniform carbon coating layer on the surface of SiO powder. If the thermal deposition temperature is too low, the pyrolysis of the gaseous carbon source will be insufficient, and if the pyrolysis temperature is too high, it will cause a disproportionation reaction in the SiO powder. , and reduce activity.
  • the temperature rise rate during vapor deposition is preferably 3 ⁇ 8°C/min.
  • the gaseous carbon source is at least one of natural gas, ethane, ethylene, propylene, and acetylene. These gaseous carbon sources are common gaseous carbon sources in the CVD deposition process.
  • the mass ratio of the carbon-coated SiO composite material to lithium tetrafluoroborate and oxalic acid is 100: 2 ⁇ 10: 1 ⁇ 20.
  • the battery will preferentially form a layer of SEI passivation film on the surface of the anode during the charge and discharge process, passivating the reaction between the anode material and the electrolyte, and reducing the consumption of active lithium; Since the SiO/C material will continue to expand and contract during the charge and discharge process, the purification membrane will continue to break, repair, break, and repair again, resulting in continuous consumption of active lithium; the coated lithium difluoroxalate borate participates in SEI Film formation will form a stable and dense SEI passivation film that is not easy to break.
  • the mass ratio of the carbon-coated SiO composite material to lithium tetrafluoroborate and oxalic acid is preferably 100:2 ⁇ 10:2 ⁇ 15.
  • the mass of the anhydrous aluminum chloride is 0.2% to 2% of the mass of lithium tetrafluoroborate.
  • Anhydrous aluminum chloride mainly catalyzes the chemical reaction between oxalic acid and lithium tetrafluoroborate.
  • the reaction conditions are: temperature is 0°C ⁇ 20°C, and time is 0.5 ⁇ 10h.
  • oxalic acid reacts with lithium tetrafluoroborate under the catalysis of anhydrous aluminum chloride to form lithium difluoroxalate borate, which crystallizes and deposits on the surface of SiO/C particles at low temperature.
  • the conditions for the static crystallization are: the temperature is greater than -40°C and less than 0°C, and the time is 0.5 to 10 hours.
  • the lower the crystallization temperature the better the crystallization effect of lithium difluoroxalate borate, and thus the better the coating effect on SiO/C materials.
  • the longer the crystallization time the more complete the crystallization will be.
  • temperature is the main factor affecting crystallization. The lower the temperature, the shorter the time required. However, above 10°C, even if the time is extended, it is difficult to obtain the ideal crystallization effect.
  • the temperature is further preferably -30°C to -10°C, and the time is preferably 3 to 6 hours.
  • the drying adopts vacuum drying
  • the drying temperature is 60°C to 120°C
  • the drying time is 4 to 24 hours.
  • the organic solution of lithium tetrafluoroborate is an ethyl acetate solution of lithium tetrafluoroborate.
  • the invention also provides a lithium difluoroxalate borate doped and coated SiO/C composite material, which is obtained by the preparation method.
  • the lithium difluoroborate doped and coated SiO/C composite material provided by the invention has a uniform CVD pyrolytic carbon layer on the surface of the SiO material, which not only effectively increases the conductivity of the SiO material, but also can prevent the expansion process of the SiO material. It plays a buffering role and also provides a large number of active sites for the doping and deposition of lithium difluoroxaloborate, thereby forming a uniform lithium difluoroxaloborate coating layer in situ outside the carbon layer, using lithium difluoroxaloborate.
  • a stable and dense SEI film is formed on the surface of the negative electrode, which can effectively reduce the frequency of rupture and reorganization of the SEI film, reduce the consumption of active lithium, and greatly improve the Coulombic efficiency and cycle life of the negative electrode material.
  • the invention also provides an application of lithium difluoroxaloborate doped and coated SiO/C composite material, which is used as a negative electrode material for lithium ion batteries.
  • the lithium difluoroxaloborate-doped and modified SiO/C composite material (SiO/C@LiODFB) of the present invention is used in lithium ion batteries: the lithium difluoroxaloxaloborate-doped and modified SiO/C composite material, according to the mass Percent composition: SiO/C@LiODFB composite material (84.5 ⁇ 95%): Conductive agent SP (3 ⁇ 10%): Binder PVDF (2 ⁇ 5.5%) is mixed in the proportion, add NMP and stir evenly to prepare a viscosity of 3500 ⁇ 5000cps slurry, and then assembled into button cells with lithium sheets in a glove box.
  • the 18650 cylindrical battery is assembled on the 18650 cylindrical battery line for cycle performance testing.
  • the SiO/C@LiODFB composite material provided by the present invention has a uniform CVD pyrolytic carbon layer on the surface of the SiO material, which not only effectively increases the conductivity of the SiO material, but also plays a buffering role in the expansion process of the SiO material, while also Provides a large number of active sites for the doping and deposition of lithium difluoroxaloborate, thereby forming a uniform lithium difluoroxaloborate coating layer in situ outside the carbon layer.
  • the lithium difluoroxaloborate is used in the battery charging and discharging process.
  • a stable and dense SEI film is formed on the surface of the negative electrode, which reduces the continuous rupture and repair of the SEI film caused by the expansion and contraction of SiO particles. It continuously and effectively slows down the consumption of lithium source by the SEI film, while reducing the generation of lithium dendrites and increasing battery life. The service life of the material.
  • the preparation method of the SiO/C@LiODFB composite material provided by the present invention is simple to operate and is conducive to large-scale production.
  • the application of the SiO/C@LiODFB composite material provided by the present invention as an anode material for lithium ion batteries can effectively improve the Coulombic efficiency and cycle performance of lithium ion batteries.
  • Figure 1 is a scanning electron microscope image of the SiO/C@LiODFB composite material prepared in Example 1; it can be seen from Figure 1 that there are many nanoscale LiODFB small particles coating the surface of the SiO/C particles.
  • Figures 2 to 4 respectively show the charge and discharge curves of button cells made of SiO/C in Example 1, Example 4 and without LiODFB material coating; it can be seen from the figures that the SiO/C@LiODFB in Example 1
  • the first reversible specific capacity of the button battery made of the material was 1218.5mAh/g, and the first Coulombic efficiency was 82.93%.
  • the first reversible specific capacity was 1553.1 mAh/g, and the first Coulomb efficiency was 75.04%.
  • Figure 5 is a 200-cycle cycle diagram of the 2600mAh cylindrical battery prepared with compound graphite in Example 1 when charged at 1C and discharged at 8C. It can be seen from the figure that the capacity retention rate after 200 cycles is 93%; showing good Rate cycle performance, and the cycle performance was tested at 0.5C charge and 1C discharge. The capacity retention rate for 200 cycles was 98.3%, with very little attenuation and excellent cycle performance.
  • the preparation method of lithium difluoroxaloborate doped and modified SiO/C composite material (SiO/C@LiODFB) anode material provided in this embodiment includes the following steps:
  • Lithium tetrafluoroborate is dried in a vacuum oven at 100°C for 8 hours, and oxalic acid is dried in a vacuum drying oven at 50°C for 8 hours.
  • step 4 Place the reaction solution in step 3 in a -20°C freezing solution for 4 hours, then filter, take the filtered solid, and dry the filtered product in a vacuum drying oven at 60°C for 12 hours. That is, the SiO/C composite material (SiO/C@LiODFB) doped and modified with lithium difluoroxalate borate is obtained.
  • SiO/C composite material SiO/C@LiODFB
  • Example 1 The only difference from Example 1 is that the amount of lithium tetrafluoroborate added is 10g, the amount of oxalic acid is 11g, the amount of aluminum trichloride is 0.2g, and the reaction time is 10h.
  • Example 1 The only difference from Example 1 is that the amount of lithium tetrafluoroborate added is 2g, the amount of oxalic acid is 2g, the amount of aluminum trichloride is 0.04g, and the reaction time is 3h.
  • Example 1 The only difference from Example 1 is that only the crystallization temperature and crystallization time were changed.
  • the crystallization temperature was 10°C and the crystallization time was 10 hours.
  • Example 1 The only difference from Example 1 is that only the crystallization temperature and crystallization time were changed.
  • the crystallization temperature was 0°C and the crystallization time was 6 hours.
  • Example 1 The only difference from Example 1 is that only the crystallization temperature and crystallization time were changed.
  • the crystallization temperature was -10°C and the crystallization time was 6 hours.
  • Example 1 The only difference from Example 1 is that only the crystallization temperature and crystallization time were changed.
  • the crystallization temperature was -40°C and the crystallization time was 4 hours.
  • the composite materials obtained in the above seven examples were made into button batteries, and the SiO/C material with a carbon content of 4.29% in Example 1 was also used to assemble into button batteries for electrochemical performance testing:
  • the materials are all proportioned according to the ratio of SiO/C@LiODFB (86.5%): conductive agent SP (10%): binder PVDF (3.5%).
  • the electrolyte is 1mol/L LiPF6/(EC+DMC)
  • the separator is Celgard2400 membrane.
  • the SiO/C@LiODFB material in Example 1 is compounded with graphite to form a composite material with a gram capacity of 420mAh/g, and is assembled together with the ternary cathode high-nickel 811 material to form a cylindrical battery.
  • the cylindrical battery is designed to be: 0.2C nominal
  • the capacity is 2600mAh.
  • the high-rate cycle performance is tested at a 1C rate and a 8C rate discharge.
  • the capacity retention rate is 93% after 200 cycles; showing good rate cycle performance.
  • the cycle performance was tested at 0.5C charge and 1C discharge, and the capacity retention rate for 200 cycles was 98.3%, with very little attenuation and excellent cycle performance.
  • Figure 1 is the SEM characterization picture of SiO/C@LiODFB material.
  • Figures 2 to 4 are respectively the charge and discharge curves of Example 1, Example 4, and SiO/C material button batteries with a carbon content of 4.29% at 25°C and a 0.1C rate.
  • Figure 5 is a cycle diagram of a 2600mAh cylindrical battery made of composite graphite in Example 1 when charged at 1C and discharged at 8C.
  • the SiO/C@LiODFB material of Example 1 made a button cell with a first reversible specific capacity of 1218.5 mAh/g and a first Coulombic efficiency of 82.93%.
  • the first reversible specific capacity of the button battery made of the CVD-coated SiO/C material with a carbon content of 4.29% was 1553.1mAh/g, and the first Coulombic efficiency was 75.04%.
  • Examples 4 and 5 Because the crystallization temperature of Examples 4 and 5 is too high, no effective crystallization layer is formed on the surface of the SiO/C material. Their first Coulomb efficiencies are 75.21% and 74.88% respectively, which are similar to SiO/C without LiODFB material coating. .
  • Table 1 shows the first charge and discharge data of the SiO/C@LiODFB material button cell under the condition of 25°C and a current density of 0.5C. It can be seen from Table 1 that the low-temperature crystallization coating in the embodiment is intact.
  • the first Coulomb efficiency of the battery made of SiO/C@LiODFB material is higher than that of the battery only coated with CVD carbon.
  • the cycle performance test of cylindrical batteries its cycle performance is excellent. That is, the SiO/C@ provided by the present invention LiODFB material lithium battery anode material used in batteries can improve the cycle stability of the battery and extend the service life of the battery.

Abstract

Disclosed in the present invention are a lithium difluoro(oxalato)borate doped and coated SiO/C composite material, a preparation method therefor, and an application thereof. Vapor deposition carbon coating is performed on SiO powder in a CVD furnace; then SiO/C is taken as a core, and in-situ crystallization is performed on the SiO/C to generate a lithium difluoro(oxalato)borate coating layer, so as to obtain a lithium difluoro(oxalato)borate doped and coated SiO/C composite material. The composite material is formed by in-situ deposition and uniform coating of lithium difluoro(oxalato)borate on the surfaces of SiO/C particles. A carbon coating layer can effectively improve conductivity and provide buffering for an expansion process of a SiO material, and the lithium difluoro(oxalato)borate can form, on the surface of a negative electrode, a stable and compact SEI film that is not prone to break, thereby continuously and effectively slowing the consumption of a lithium source by the SEI film, reducing the generation of lithium dendrites, and improving the service life of a battery material and the high and low temperature performance of a battery.

Description

一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料及其制备方法和应用A kind of lithium difluoroxalate borate doped and coated SiO/C composite material and its preparation method and application 技术领域Technical field
本发明涉及一种锂离子电池负极材料；特别涉及一种二氟草酸硼酸锂掺杂SiO/C复合负极材料，还涉及一种二氟草酸硼酸锂掺杂SiO/C复合材料的制备方法和作为锂离子电池负极材料的应用，属于锂电池技术领域。The invention relates to a lithium ion battery negative electrode material; in particular, it relates to a lithium difluoroxaloborate doped SiO/C composite negative electrode material, and also relates to a preparation method and use of a lithium difluoroxaloborate doped SiO/C composite material. The application of lithium-ion battery negative electrode materials belongs to the field of lithium battery technology.
背景技术Background technique
随着便携式电子设备、无人机、电动工具和电动车的迅速发展，高能量密度、高功率密度、高安全性和长寿命的可充电电池备受关注。尽管基于传统的石墨负极材料锂离子电池取得了广泛应用，但其相对较低的理论能量密度限制了其进一步的发展。寻找石墨负极的替代材料成为当前二次电池研究的关键。With the rapid development of portable electronic devices, drones, power tools and electric vehicles, rechargeable batteries with high energy density, high power density, high safety and long life have attracted much attention. Although lithium-ion batteries based on traditional graphite anode materials have been widely used, their relatively low theoretical energy density limits their further development. Finding alternative materials for graphite anodes has become the key to current secondary battery research.
技术问题technical problem
硅是目前已知比容量（4200mAh）最高的锂离子电池负极材料，但由于其巨大的体积效应（>300%）会导致电化学性能急剧恶化。因此，体积效应较小的硅的氧化物成为了比较理想的选择。其中，氧化亚硅（SiO）体积效应（150%）较小，同时拥有较高的理论容量（>1500mAh），成为近年来锂离子电池负极材料研究的热点。Silicon is the currently known lithium-ion battery anode material with the highest specific capacity (4200mAh), but its huge volume effect (>300%) will lead to a sharp deterioration in electrochemical performance. Therefore, silicon oxides with smaller volume effects have become an ideal choice. Among them, silicon oxide (SiO) has a small volume effect (150%) and a high theoretical capacity (>1500mAh). It has become a hot topic in the research of negative electrode materials for lithium-ion batteries in recent years.
虽然氧化亚硅（SiO）体积效应较硅要小，但其循环性能和首次库仑效率较差，为改善其循环性能和提高其首次库仑效率，研究发现在氧化亚硅（SiO）表面包覆碳材料作为膨胀缓冲层，对氧化亚硅（SiO）材料进行预锂化处理能极大提高其循环性能和首次库仑效率。如：中国专利（公开号CN111900368 A）提供了一种先对SiO进行预锂化，然后进行气相沉积包碳，然后再在其表面包覆一层金属氧化物。改性碳包覆预锂化的方法，其首次库伦效率达到88%。中国专利（公开号CN109524621A）提供了一种电化学预锂的技术，通过预制硅氧材料负极极片，与金属锂片组装成半电池模型，通过电池对外放电的方式进行预锂化，预锂化后的硅氧材料的首周效率可达90％以上。中国专利（公开号CN112151771A）提供了一种硅酸盐骨架的硅基负极材料，其主要是在SiO材料中掺入Mg和Li的硅酸盐骨架，改善硅基负极的膨胀和应力来达到提高材料的循环性能的目的。 Yi-Fan Tian, Ge Li等发表的《Micron-Sized SiMgyOx with Stable Internal Structure Evolution for High-Performance Li-Ion Battery Anodes》中讨论了不同量的镁掺杂对SiO材料的影响，通过改善掺杂量和掺杂处理温度可以有效提高SiO材料的首次库仑效率和循环寿命。在以上的方法中，碳包覆可以有效改善导电性、缓冲膨胀；预锂化掺杂可形成硅酸盐骨架缓减膨胀，减少正极活性锂的消耗；这二种方法都可以一定程度上提高SiO材料的首次库仑效率和循环寿命。此外，锂电池充、放电过程中，SiO材料除了本身膨胀、收缩，导致材料出现粉化、坍塌，剥离集流体导致电池失效以外，其膨胀还会导致在负极形成的SEI膜也极不稳定，不停的破裂、重组，消耗大量的活性锂，使得电池的库仑效率和循环寿命降低。 Although the volume effect of silicon oxide (SiO) is smaller than that of silicon, its cycle performance and first Coulomb efficiency are poor. In order to improve its cycle performance and first Coulomb efficiency, research has found that the surface of silicon oxide (SiO) is coated with carbon. The material serves as an expansion buffer layer, and pre-lithiation treatment of silicon oxide (SiO) materials can greatly improve its cycle performance and first Coulombic efficiency. For example: Chinese patent (publication number CN111900368 A) provides a method of first pre-lithiating SiO, then vapor deposition carbon coating, and then coating a layer of metal oxide on its surface. The first Coulombic efficiency of the modified carbon coating prelithiation method reached 88%. Chinese patent (publication number CN109524621A) provides an electrochemical pre-lithium technology. It assembles a half-battery model by prefabricating silicon-oxygen material negative electrode sheets and metal lithium sheets, and performs pre-lithiumization through external discharge of the battery. Pre-lithium The first-week efficiency of the treated silicone material can reach more than 90%. Chinese patent (publication number CN112151771A) provides a silicon-based negative electrode material with a silicate skeleton. It mainly incorporates a silicate skeleton of Mg and Li into the SiO material to improve the expansion and stress of the silicon-based negative electrode to achieve improvement. The purpose of material recycling performance. "Micron-Sized SiMgyOx with Stable Internal Structure Evolution for High-Performance Li-Ion Battery Anodes" published by Yi-Fan Tian, Ge Li et al. discussed the impact of different amounts of magnesium doping on SiO materials. By improving the doping amount and doping treatment temperature can effectively improve the first Coulomb efficiency and cycle life of SiO materials. Among the above methods, carbon coating can effectively improve conductivity and buffer expansion; prelithiation doping can form a silicate skeleton to slow expansion and reduce the consumption of active lithium in the cathode; both methods can improve the performance to a certain extent. First Coulombic efficiency and cycle life of SiO materials. In addition, during the charging and discharging process of lithium batteries, the SiO material itself expands and contracts, causing the material to pulverize and collapse, and the current collector is peeled off, causing battery failure. Its expansion will also cause the SEI film formed on the negative electrode to be extremely unstable. Constant rupture and reorganization consumes a large amount of active lithium, which reduces the Coulombic efficiency and cycle life of the battery.
技术解决方案Technical solutions
针对现有技术存在的缺陷，本发明的第一个目的是在于提供一种二氟草酸硼酸锂掺杂SiO/C复合材料(SiO/C@LiODFB)，该复合材料由二氟草酸硼酸锂原位沉积并均匀包覆在SiO/C颗粒表面构成，碳包覆层能够有效提高氧化亚硅材料的导电性和为SiO材料的膨胀过程中提供缓冲，且二氟草酸硼酸锂在负极表面能形成稳定且致密的SEI膜，不易破裂，能够持续而有效减缓SEI膜对于锂源的消耗，同时减少锂枝晶生成，增加电池材料的使用寿命和电池的高低温性能。In view of the shortcomings of the existing technology, the first object of the present invention is to provide a lithium difluoroxaloborate-doped SiO/C composite material (SiO/C@LiODFB), which is composed of lithium difluoroxaloborate. It is deposited and uniformly coated on the surface of SiO/C particles. The carbon coating layer can effectively improve the conductivity of the silicon oxide material and provide a buffer for the expansion process of the SiO material, and lithium difluoroxalate borate can form on the surface of the negative electrode. The stable and dense SEI film is not easy to break, and can continuously and effectively slow down the consumption of lithium source by the SEI film, while reducing the formation of lithium dendrites, increasing the service life of battery materials and the high and low temperature performance of the battery.
本发明的第二个目的是在于提供一种二氟草酸硼酸锂掺杂SiO/C复合材料的制备方法，该制备方法操作简单，成本低，适合大规模生产。The second object of the present invention is to provide a preparation method of lithium difluoroxaloborate-doped SiO/C composite material, which is simple to operate, low in cost, and suitable for large-scale production.
本发明的第三个目的是在于提供一种二氟草酸硼酸锂掺杂SiO/C复合材料作为锂离子电池负极材料的应用，将其应用在锂离子电池中可以有效提高锂离子电池的库伦效率和循环性能。The third object of the present invention is to provide a lithium difluoroxaloborate-doped SiO/C composite material as an anode material for lithium ion batteries. Its application in lithium ion batteries can effectively improve the Coulombic efficiency of lithium ion batteries. and cycle performance.
为了实现上述技术目的，本发明提供了一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，该方法包括以下步骤：In order to achieve the above technical objectives, the present invention provides a method for preparing a lithium difluoroxalate borate doped and coated SiO/C composite material, which method includes the following steps:
1）通过CVD气相沉积在SiO粉体表面生成碳包覆层，得到碳包覆SiO复合材料；1) Generate a carbon coating layer on the surface of SiO powder through CVD vapor deposition to obtain a carbon-coated SiO composite material;
2）将草酸溶于四氟硼酸锂有机溶液后，加入碳包覆SiO复合材料，再在搅拌条件下缓慢滴加无水氯化铝进行反应，反应完毕后，依次进行静置结晶、过滤和干燥，即得二氟草酸硼酸锂掺杂包覆SiO/C复合材料。2) After dissolving oxalic acid in the organic solution of lithium tetrafluoroborate, add the carbon-coated SiO composite material, and then slowly add anhydrous aluminum chloride dropwise under stirring conditions to react. After the reaction is completed, proceed with static crystallization, filtration and After drying, the lithium difluoroxalate borate doped and coated SiO/C composite material is obtained.
本发明技术方案先以SiO材料为核，通过CVD方法在SiO材料外表面包覆一层均匀碳层，该均匀碳包覆层不但能够有效增加SiO材料的导电性，而且能够对SiO材料的膨胀过程中进行缓冲，此外还为二氟草酸硼酸锂的沉积和掺杂提供大量的活性位点，有利于在碳层外面均匀、原位掺杂和包覆二氟草酸硼酸锂，而SiO/C表面包覆的二氟草酸硼酸锂在锂电池运行过程中能在负极表面形成稳定且致密的SEI膜，能有效降低SEI膜的破裂、重组频次，减少活性锂的消耗，大幅度提高材料的库仑效率和循环寿命。The technical solution of the present invention first uses SiO material as the core, and coats the outer surface of the SiO material with a uniform carbon layer through the CVD method. This uniform carbon coating layer can not only effectively increase the conductivity of the SiO material, but also can reduce the expansion of the SiO material. Buffering is provided during the process. In addition, it also provides a large number of active sites for the deposition and doping of lithium difluoroxaloborate, which is conducive to uniform and in-situ doping and coating of lithium difluoroxaloborate outside the carbon layer, while SiO/C The surface-coated lithium difluoroxalate borate can form a stable and dense SEI film on the surface of the negative electrode during the operation of the lithium battery, which can effectively reduce the rupture and reorganization frequency of the SEI film, reduce the consumption of active lithium, and greatly increase the Coulomb density of the material. efficiency and cycle life.
作为一个优选的方案，所述SiO粉体的粒径D50为3~8μm。As a preferred solution, the particle size D50 of the SiO powder is 3~8 μm.
作为一个优选的方案，所述CVD气相沉积的条件为：气体碳源流量为0.5~5 L/min，温度为600~950℃，时间为0.5~5h。在优选的条件下有利于在SiO粉体表面生成均匀的碳包覆层，热沉积温度如果偏低导致气体碳源热解不充分，而热解温度过高则会造成SiO粉体发生歧化反应，而降低活性。气相沉积过程中升温速率优选为3~8℃/min。As a preferred solution, the conditions for the CVD vapor deposition are: gas carbon source flow rate is 0.5~5 L/min, temperature is 600~950℃, time is 0.5~5h. Under optimal conditions, it is beneficial to generate a uniform carbon coating layer on the surface of SiO powder. If the thermal deposition temperature is too low, the pyrolysis of the gaseous carbon source will be insufficient, and if the pyrolysis temperature is too high, it will cause a disproportionation reaction in the SiO powder. , and reduce activity. The temperature rise rate during vapor deposition is preferably 3~8°C/min.
作为一个优选的方案，所述气体碳源为天燃气、乙烷、乙烯、丙烯、乙炔中至少一种。这些气体碳源都是CVD沉积过程中常见的气体碳源。As a preferred solution, the gaseous carbon source is at least one of natural gas, ethane, ethylene, propylene, and acetylene. These gaseous carbon sources are common gaseous carbon sources in the CVD deposition process.
作为一个优选的方案，所述碳包覆SiO复合材料与四氟硼酸锂及草酸的质量比为100 : 2~10 : 1~20。SiO/C@LiODFB复合材料用于锂离子负极材料后，电池在充放电过程中会优先在负极表面形成一层SEI钝化膜，钝化负极材料与电解液的反应，减少活性锂的消耗；由于SiO/C材料在充放电过程中会不断的膨胀、收缩，导致纯化膜不断的破裂、修复、再破裂、再修复，对活性锂形成持续的消耗；包覆的二氟草酸硼酸锂参与SEI成膜，会形成稳定且致密的SEI钝化膜，不易破裂。如果二氟草酸硼酸锂包覆量过少，对SEI钝化膜不能形成持续的维持；包覆量过多，会降低电池材料本身的克容量。碳包覆SiO复合材料与四氟硼酸锂及草酸的质量比优选为100 : 2~10 : 2~15。As a preferred solution, the mass ratio of the carbon-coated SiO composite material to lithium tetrafluoroborate and oxalic acid is 100: 2~10: 1~20. After the SiO/C@LiODFB composite material is used as a lithium-ion anode material, the battery will preferentially form a layer of SEI passivation film on the surface of the anode during the charge and discharge process, passivating the reaction between the anode material and the electrolyte, and reducing the consumption of active lithium; Since the SiO/C material will continue to expand and contract during the charge and discharge process, the purification membrane will continue to break, repair, break, and repair again, resulting in continuous consumption of active lithium; the coated lithium difluoroxalate borate participates in SEI Film formation will form a stable and dense SEI passivation film that is not easy to break. If the coating amount of lithium difluoroxalate borate is too small, the SEI passivation film cannot be maintained continuously; if the coating amount is too much, the gram capacity of the battery material itself will be reduced. The mass ratio of the carbon-coated SiO composite material to lithium tetrafluoroborate and oxalic acid is preferably 100:2~10:2~15.
作为一个优选的方案，所述无水氯化铝的质量为四氟硼酸锂质量的0.2%~2%。无水氯化铝主要起到催化草酸与四氟硼酸锂之间的化学反应。As a preferred solution, the mass of the anhydrous aluminum chloride is 0.2% to 2% of the mass of lithium tetrafluoroborate. Anhydrous aluminum chloride mainly catalyzes the chemical reaction between oxalic acid and lithium tetrafluoroborate.
作为一个优选的方案，所述反应的条件为：温度为0℃~20℃，时间为0.5~10h。在优选的反应条件下草酸与四氟硼酸锂在无水氯化铝的催化作用下反应生成二氟草酸硼酸锂，并低温下结晶沉积在SiO/C颗粒表面。As a preferred solution, the reaction conditions are: temperature is 0°C~20°C, and time is 0.5~10h. Under the preferred reaction conditions, oxalic acid reacts with lithium tetrafluoroborate under the catalysis of anhydrous aluminum chloride to form lithium difluoroxalate borate, which crystallizes and deposits on the surface of SiO/C particles at low temperature.
作为一个优选的方案，所述静置结晶的条件为：温度为大于-40℃，且小于0℃，时间为0.5~10h。结晶温度越低，二氟草酸硼酸锂的结晶效果越好，从而对SiO/C材料的包覆效果也更好。而结晶时间理论上来说，时间越长结晶更完全，但实际上温度是影响结晶的主要因素，温度越低所要求的时间越短。但是在10℃度以上，就算时间拉长，也很难获得理想的结晶效果，但是如果结晶温度过低，结晶速度太快，容易形成大颗粒晶粒或晶堆，形成不了很好的包覆层。因此，温度进一步优选为-30℃~-10℃，时间优选为3~6h。As a preferred solution, the conditions for the static crystallization are: the temperature is greater than -40°C and less than 0°C, and the time is 0.5 to 10 hours. The lower the crystallization temperature, the better the crystallization effect of lithium difluoroxalate borate, and thus the better the coating effect on SiO/C materials. In theory, the longer the crystallization time, the more complete the crystallization will be. However, in fact, temperature is the main factor affecting crystallization. The lower the temperature, the shorter the time required. However, above 10°C, even if the time is extended, it is difficult to obtain the ideal crystallization effect. However, if the crystallization temperature is too low and the crystallization speed is too fast, it is easy to form large grains or crystal piles, and good coating cannot be formed. layer. Therefore, the temperature is further preferably -30°C to -10°C, and the time is preferably 3 to 6 hours.
作为一个优选的方案，所述干燥采用真空干燥，干燥的温度为60℃~120℃，干燥时间为4~24h。As a preferred solution, the drying adopts vacuum drying, the drying temperature is 60°C to 120°C, and the drying time is 4 to 24 hours.
作为一个优选的方案，所述四氟硼酸锂有机溶液为四氟硼酸锂的乙酸乙酯溶液。As a preferred solution, the organic solution of lithium tetrafluoroborate is an ethyl acetate solution of lithium tetrafluoroborate.
本发明还提供了一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料，其由所述的制备方法得到。The invention also provides a lithium difluoroxalate borate doped and coated SiO/C composite material, which is obtained by the preparation method.
本发明提供的二氟草酸硼酸锂掺杂包覆SiO/C复合材料在SiO材料表面具有均匀的CVD热解碳层，不但有效增加了SiO材料的导电性，而且能够对SiO材料的膨胀过程中起到缓冲作用，同时还为二氟草酸硼酸锂的掺杂和沉积提供大量的活性位点，从而在碳层外面原位形成均匀的二氟草酸硼酸锂包覆层，利用二氟草酸硼酸锂在电池充放电过程中在负极表面形成稳定且致密的SEI膜，能有效降低SEI膜的破裂、重组频次，减少活性锂的消耗，大幅度提高负极材料的库仑效率和循环寿命。The lithium difluoroborate doped and coated SiO/C composite material provided by the invention has a uniform CVD pyrolytic carbon layer on the surface of the SiO material, which not only effectively increases the conductivity of the SiO material, but also can prevent the expansion process of the SiO material. It plays a buffering role and also provides a large number of active sites for the doping and deposition of lithium difluoroxaloborate, thereby forming a uniform lithium difluoroxaloborate coating layer in situ outside the carbon layer, using lithium difluoroxaloborate. During the battery charge and discharge process, a stable and dense SEI film is formed on the surface of the negative electrode, which can effectively reduce the frequency of rupture and reorganization of the SEI film, reduce the consumption of active lithium, and greatly improve the Coulombic efficiency and cycle life of the negative electrode material.
本发明还提供了一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的应用，其作为锂离子电池负极材料应用。The invention also provides an application of lithium difluoroxaloborate doped and coated SiO/C composite material, which is used as a negative electrode material for lithium ion batteries.
本发明的二氟草酸硼酸锂掺杂改性的SiO/C复合材料(SiO/C@LiODFB)用于锂离子电池：将二氟草酸硼酸锂掺杂改性的SiO/C复合材料，按质量百分比组成：SiO/C@LiODFB复合材料（84.5~95%）: 导电剂SP（3~10%）: 粘结剂PVDF（2~5.5%）的比例混合，加入NMP搅拌均匀，配成粘度3500~5000cps的浆料，然后在手套箱中与锂片组装成扣式电池。在18650圆柱电池线上组装成18650圆柱电池进行循环性能测试。The lithium difluoroxaloborate-doped and modified SiO/C composite material (SiO/C@LiODFB) of the present invention is used in lithium ion batteries: the lithium difluoroxaloxaloborate-doped and modified SiO/C composite material, according to the mass Percent composition: SiO/C@LiODFB composite material (84.5~95%): Conductive agent SP (3~10%): Binder PVDF (2~5.5%) is mixed in the proportion, add NMP and stir evenly to prepare a viscosity of 3500 ~5000cps slurry, and then assembled into button cells with lithium sheets in a glove box. The 18650 cylindrical battery is assembled on the 18650 cylindrical battery line for cycle performance testing.
有益效果beneficial effects
本发明提供的SiO/C@LiODFB复合材料在SiO材料表面具有均匀的CVD热解碳层，不但有效增加了SiO材料的导电性，而且能够对SiO材料的膨胀过程中起到缓冲作用，同时还为二氟草酸硼酸锂的掺杂和沉积提供大量的活性位点，从而在碳层外面原位形成均匀的二氟草酸硼酸锂包覆层，利用二氟草酸硼酸锂在电池充放电过程中于负极表面形成稳定且致密的SEI膜，降低由于SiO颗粒在膨胀和收缩过程中引起的SEI膜不断的破裂、修复，持续有效的减缓SEI膜对于锂源的消耗，同时减少锂晶枝生成，增加电池材料的使用寿命。The SiO/C@LiODFB composite material provided by the present invention has a uniform CVD pyrolytic carbon layer on the surface of the SiO material, which not only effectively increases the conductivity of the SiO material, but also plays a buffering role in the expansion process of the SiO material, while also Provides a large number of active sites for the doping and deposition of lithium difluoroxaloborate, thereby forming a uniform lithium difluoroxaloborate coating layer in situ outside the carbon layer. The lithium difluoroxaloborate is used in the battery charging and discharging process. A stable and dense SEI film is formed on the surface of the negative electrode, which reduces the continuous rupture and repair of the SEI film caused by the expansion and contraction of SiO particles. It continuously and effectively slows down the consumption of lithium source by the SEI film, while reducing the generation of lithium dendrites and increasing battery life. The service life of the material.
本发明的提供的SiO/C@LiODFB复合材料的制备方法操作简单、有利于大规模生产。The preparation method of the SiO/C@LiODFB composite material provided by the present invention is simple to operate and is conducive to large-scale production.
本发明的提供的SiO/C@LiODFB复合材料作为锂离子电池负极材料的应用，可以有效提高锂离子电池的库伦效率和循环性能。The application of the SiO/C@LiODFB composite material provided by the present invention as an anode material for lithium ion batteries can effectively improve the Coulombic efficiency and cycle performance of lithium ion batteries.
附图说明Description of the drawings
图1为实施例1制备的SiO/C@LiODFB复合材料扫描电镜图；从图1中可以看出，在SiO/C颗粒表面有很多纳米级的LiODFB小颗粒包覆。Figure 1 is a scanning electron microscope image of the SiO/C@LiODFB composite material prepared in Example 1; it can be seen from Figure 1 that there are many nanoscale LiODFB small particles coating the surface of the SiO/C particles.
图2~图4分别为实施例1、实施例4和没有包覆LiODFB材料的SiO/C制成扣式电池的充放电曲线；从图中可以看出，实施例1的SiO/C@LiODFB材料做成扣式电池首次可逆比容量为1218.5mAh/g，首次库伦效率为82.93％，对比没包覆LiODFB材料，只用CVD包覆碳含量为4.29%的SiO/C材料做成扣式电池首次可逆比容量为1553.1mAh/g，首次库伦效率为75.04％；实施例4和实施例5由于结晶温度太高，在SiO/C材料表面并没有形成有效的结晶层，其首次库仑效率分别为75.21%和74.88%，与没有包覆LiODFB材料的SiO/C差不多。Figures 2 to 4 respectively show the charge and discharge curves of button cells made of SiO/C in Example 1, Example 4 and without LiODFB material coating; it can be seen from the figures that the SiO/C@LiODFB in Example 1 The first reversible specific capacity of the button battery made of the material was 1218.5mAh/g, and the first Coulombic efficiency was 82.93%. Compared with the uncoated LiODFB material, only the CVD-coated SiO/C material with a carbon content of 4.29% was used to make the button battery. The first reversible specific capacity was 1553.1 mAh/g, and the first Coulomb efficiency was 75.04%. Due to the high crystallization temperature, no effective crystallization layer was formed on the surface of the SiO/C material in Examples 4 and 5, and their first Coulomb efficiencies were respectively 75.21% and 74.88%, which are similar to SiO/C without LiODFB material coating.
图5为实施例1复配石墨制备的2600mAh圆柱电池1C充电，8C放电情况下的200周循环图；从图中可以看出，循环200周后容量保持率为93%；显示出很好的倍率循环性能，而以0.5C充1C放电测试循环性能，200周容量保持率为98.3%，衰减很小，循环性能优异。Figure 5 is a 200-cycle cycle diagram of the 2600mAh cylindrical battery prepared with compound graphite in Example 1 when charged at 1C and discharged at 8C. It can be seen from the figure that the capacity retention rate after 200 cycles is 93%; showing good Rate cycle performance, and the cycle performance was tested at 0.5C charge and 1C discharge. The capacity retention rate for 200 cycles was 98.3%, with very little attenuation and excellent cycle performance.
本发明的实施方式Embodiments of the invention
下面结合具体实施例对本发明作进一步详细的描述，但本发明的实施方式不限于此。The present invention will be described in further detail below with reference to specific examples, but the implementation of the present invention is not limited thereto.
如无特别说明，以下实施例中所有原料和试剂均为市购常规的原料和试剂。Unless otherwise specified, all raw materials and reagents in the following examples are commercially available conventional raw materials and reagents.
实施例Example 11
本实施例提供的二氟草酸硼酸锂掺杂改性的SiO/C复合材料（SiO/C@LiODFB）负极材料的制备方法，包括如下步骤：The preparation method of lithium difluoroxaloborate doped and modified SiO/C composite material (SiO/C@LiODFB) anode material provided in this embodiment includes the following steps:
1）称取D50在5μm左右的SiO粉体2000g装入CVD转炉中，调节转炉速度至15转/min，以0.5L/min的流量通入氮气1h，然后通入天燃气，天燃气的流量为2L/min，然后以5℃/min的速率升温至950℃，950℃恒温2h，自然降温至常温.获得表面碳包覆的SiO/C材料，通过碳硫仪测试，碳包覆量为4.29%。1) Weigh 2000g of SiO powder with a D50 of about 5 μm and put it into the CVD converter. Adjust the converter speed to 15 rpm, flow in nitrogen at a flow rate of 0.5L/min for 1 hour, and then flow in natural gas. The flow rate of natural gas is 2L/min, and then the temperature is raised to 950°C at a rate of 5°C/min, held at 950°C for 2 hours, and then naturally cooled to normal temperature. The SiO/C material coated with carbon on the surface is obtained and tested by a carbon sulfur meter. The amount of carbon coating is 4.29%.
2）四氟硼酸锂在100℃真空烘箱中干燥8h，草酸在50℃真空干燥箱中干燥8h。2) Lithium tetrafluoroborate is dried in a vacuum oven at 100°C for 8 hours, and oxalic acid is dried in a vacuum drying oven at 50°C for 8 hours.
3）称取干燥过的四氟硼酸锂6g，溶解于乙酸乙酯中，加入6g草酸，搅拌直到完全溶解，保持搅拌，加入步骤1中获得的SiO/C材料100g，继续搅拌10min，然后加入0.1g三氯化铝反应4h。3) Weigh 6g of dried lithium tetrafluoroborate, dissolve it in ethyl acetate, add 6g of oxalic acid, stir until completely dissolved, keep stirring, add 100g of SiO/C material obtained in step 1, continue stirring for 10 minutes, and then add 0.1g aluminum trichloride reacted for 4 hours.
4）将步骤3中的反应液置于-20℃的冷冻液中静置4h，然后过滤，取过滤后的固体，将过滤后的产品在真空干燥箱中60℃干燥12h。即得二氟草酸硼酸锂掺杂改性的SiO/C复合材料（SiO/C@LiODFB）。4) Place the reaction solution in step 3 in a -20°C freezing solution for 4 hours, then filter, take the filtered solid, and dry the filtered product in a vacuum drying oven at 60°C for 12 hours. That is, the SiO/C composite material (SiO/C@LiODFB) doped and modified with lithium difluoroxalate borate is obtained.
实施例Example 22
与实施例1的区别仅在于：只是加入四氟硼酸锂量为10g，草酸用量为11g，三氯化铝的量为0.2g，反应时间为10h。The only difference from Example 1 is that the amount of lithium tetrafluoroborate added is 10g, the amount of oxalic acid is 11g, the amount of aluminum trichloride is 0.2g, and the reaction time is 10h.
实施例Example 33
与实施例1的区别仅在于：只是加入四氟硼酸锂量为2g，草酸用量为2g，三氯化铝的量为0.04g，反应时间为3h。The only difference from Example 1 is that the amount of lithium tetrafluoroborate added is 2g, the amount of oxalic acid is 2g, the amount of aluminum trichloride is 0.04g, and the reaction time is 3h.
实施例Example 44 （对照实例）(Contrast example)
与实施例1的区别仅在于：只是结晶温度与结晶时间改变，结晶温度为10℃，结晶时间为10h。The only difference from Example 1 is that only the crystallization temperature and crystallization time were changed. The crystallization temperature was 10°C and the crystallization time was 10 hours.
实施例Example 55 （对照实例）(Contrast example)
与实施例1的区别仅在于：只是结晶温度与结晶时间改变，结晶温度为0℃，结晶时间为6h。The only difference from Example 1 is that only the crystallization temperature and crystallization time were changed. The crystallization temperature was 0°C and the crystallization time was 6 hours.
实施例Example 66
与实施例1的区别仅在于：只是结晶温度与结晶时间改变，结晶温度为-10℃，结晶时间为6h。The only difference from Example 1 is that only the crystallization temperature and crystallization time were changed. The crystallization temperature was -10°C and the crystallization time was 6 hours.
实施例Example 77
与实施例1的区别仅在于：只是结晶温度与结晶时间改变，结晶温度为-40℃，结晶时间为4h。The only difference from Example 1 is that only the crystallization temperature and crystallization time were changed. The crystallization temperature was -40°C and the crystallization time was 4 hours.
将上述7个实施例所得复合材料分别做成扣式电池，同时选用实施例1中的碳含量为4.29%的SiO/C材料也组装成扣式电池进行电化学性能测试：将上述实施例所得材料都按SiO/C@LiODFB（86.5%）: 导电剂SP（10%）: 粘结剂PVDF（3.5%）的比例配比，先将PVDF溶解于NMP溶剂中，然后加入导电剂SP和SiO/C@ LiODFB，混合均匀，涂膜，切片，在手套箱中组装成2025扣式锂离子电池。电解液为1mol/L的LiPF6/(EC+DMC) ，隔膜为Celgard2400膜。The composite materials obtained in the above seven examples were made into button batteries, and the SiO/C material with a carbon content of 4.29% in Example 1 was also used to assemble into button batteries for electrochemical performance testing: The materials are all proportioned according to the ratio of SiO/C@LiODFB (86.5%): conductive agent SP (10%): binder PVDF (3.5%). First dissolve PVDF in NMP solvent, then add conductive agent SP and SiO /C@ LiODFB, mix evenly, coat, slice, and assemble into 2025 button lithium-ion battery in the glove box. The electrolyte is 1mol/L LiPF6/(EC+DMC) , the separator is Celgard2400 membrane.
   采用武汉蓝电电子公司LANHE电池程控测试仪对组装的电池进行了恒电流充放电实验，实验结果列于表1中。A constant current charging and discharging experiment was conducted on the assembled battery using the LANHE battery program-controlled tester of Wuhan Landian Electronics Company. The experimental results are listed in Table 1.
   将实施例1中SiO/C@LiODFB材料复配石墨，配成克容量为420mAh/g的复合材料，与三元正极高镍811材料一起组装成圆柱电池，圆柱电池设计为：0.2C标称容量2600mAh，以1C倍率进行充电、8C倍率进行放电测试高倍率循环性能，循环200周后容量保持率为93%；显示出很好的倍率循环性能。而以0.5C充1C放电测试循环性能，200周容量保持率为98.3%，衰减很小，循环性能优异。The SiO/C@LiODFB material in Example 1 is compounded with graphite to form a composite material with a gram capacity of 420mAh/g, and is assembled together with the ternary cathode high-nickel 811 material to form a cylindrical battery. The cylindrical battery is designed to be: 0.2C nominal The capacity is 2600mAh. The high-rate cycle performance is tested at a 1C rate and a 8C rate discharge. The capacity retention rate is 93% after 200 cycles; showing good rate cycle performance. The cycle performance was tested at 0.5C charge and 1C discharge, and the capacity retention rate for 200 cycles was 98.3%, with very little attenuation and excellent cycle performance.
附图：图1为SiO/C@LiODFB材料的SEM表征图。图2~图4分别为实施例1、实施例4、以及碳含量为4.29%的SiO/C材料扣式电池在25℃条件下，0.1C倍率下的充放电曲线图。图5为实施例1复配石墨做成2600mAh圆柱电池1C充电，8C放电情况下的循环图。Attached Figures: Figure 1 is the SEM characterization picture of SiO/C@LiODFB material. Figures 2 to 4 are respectively the charge and discharge curves of Example 1, Example 4, and SiO/C material button batteries with a carbon content of 4.29% at 25°C and a 0.1C rate. Figure 5 is a cycle diagram of a 2600mAh cylindrical battery made of composite graphite in Example 1 when charged at 1C and discharged at 8C.
实施例1的SiO/C@LiODFB材料做成扣式电池首次可逆比容量为1218.5 mAh/g，首次库伦效率为82.93％。对比没包覆LiODFB材料，只用CVD包覆碳含量为4.29%的SiO/C材料做成扣式电池首次可逆比容量为1553.1mAh/g，首次库伦效率为75.04％。 The SiO/C@LiODFB material of Example 1 made a button cell with a first reversible specific capacity of 1218.5 mAh/g and a first Coulombic efficiency of 82.93%. Compared with the uncoated LiODFB material, the first reversible specific capacity of the button battery made of the CVD-coated SiO/C material with a carbon content of 4.29% was 1553.1mAh/g, and the first Coulombic efficiency was 75.04%.
实施例4和实施例5由于结晶温度太高，在SiO/C材料表面并没有形成有效的结晶层，其首次库仑效率分别为75.21%和74.88%，与没有包覆LiODFB材料的SiO/C差不多。Because the crystallization temperature of Examples 4 and 5 is too high, no effective crystallization layer is formed on the surface of the SiO/C material. Their first Coulomb efficiencies are 75.21% and 74.88% respectively, which are similar to SiO/C without LiODFB material coating. .
表1为SiO/C@LiODFB材料扣式电池在25℃条件下，0.5C电流密度下，上述前实施例的首次充放电数据，从表1中可以看出，实施例中低温结晶包覆完好的SiO/C@LiODFB材料做成的电池首次库仑效率比只做了CVD碳包覆的要高。通过圆柱电池的循环性能测试，其循环性能优异。即本发明提供的SiO/C@ LiODFB材料锂电池负极材料应用于电池中可提高电池的循环稳定性，延长电池的使用寿命。Table 1 shows the first charge and discharge data of the SiO/C@LiODFB material button cell under the condition of 25°C and a current density of 0.5C. It can be seen from Table 1 that the low-temperature crystallization coating in the embodiment is intact. The first Coulomb efficiency of the battery made of SiO/C@LiODFB material is higher than that of the battery only coated with CVD carbon. Through the cycle performance test of cylindrical batteries, its cycle performance is excellent. That is, the SiO/C@ provided by the present invention LiODFB material lithium battery anode material used in batteries can improve the cycle stability of the battery and extend the service life of the battery.

Claims (10)

  1. 一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，其特征在于：包括以下步骤：A method for preparing lithium difluoroxaloborate doped and coated SiO/C composite material, which is characterized by: including the following steps:
    1）通过CVD气相沉积在SiO粉体表面生成碳包覆层，得到碳包覆SiO复合材料；1) Generate a carbon coating layer on the surface of SiO powder through CVD vapor deposition to obtain a carbon-coated SiO composite material;
    2）将草酸溶于四氟硼酸锂有机溶液后，加入碳包覆SiO复合材料，再在搅拌条件下缓慢滴加无水氯化铝进行反应，反应完毕后，依次进行静置结晶、过滤和干燥，即得二氟草酸硼酸锂掺杂包覆SiO/C复合材料。2) After dissolving oxalic acid in the organic solution of lithium tetrafluoroborate, add the carbon-coated SiO composite material, and then slowly add anhydrous aluminum chloride dropwise under stirring conditions to react. After the reaction is completed, proceed with static crystallization, filtration and After drying, the lithium difluoroxalate borate doped and coated SiO/C composite material is obtained.
  2. 根据权利要求1所述的一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，其特征在于：所述SiO粉体的粒径D50为3~8μm。The preparation method of lithium difluoroxaloborate doped and coated SiO/C composite material according to claim 1, characterized in that: the particle size D50 of the SiO powder is 3 to 8 μm.
  3. 根据权利要求1所述的一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，其特征在于：所述CVD气相沉积的条件为：气体碳源流量为0.5~5L/min，温度为600~950℃，时间为0.5~5h。A method for preparing lithium difluoroxaloborate doped and coated SiO/C composite material according to claim 1, characterized in that: the conditions of the CVD vapor deposition are: the gas carbon source flow rate is 0.5~5L/min , temperature is 600~950℃, time is 0.5~5h.
  4. 根据权利要求3所述的一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，其特征在于：所述气体碳源为天燃气、乙烷、乙烯、丙烯、乙炔中至少一种。A method for preparing lithium difluoroxaloborate doped and coated SiO/C composite materials according to claim 3, characterized in that: the gaseous carbon source is at least one of natural gas, ethane, ethylene, propylene and acetylene. A sort of.
  5. 根据权利要求1所述的一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，其特征在于：所述碳包覆SiO复合材料与四氟硼酸锂及草酸的质量比为100 : 2~10 : 1~20。A method for preparing a lithium difluoroborate doped coated SiO/C composite material according to claim 1, characterized in that: the mass ratio of the carbon coated SiO composite material to lithium tetrafluoroborate and oxalic acid is 100: 2~10: 1~20.
  6. 根据权利要求1所述的一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，其特征在于：所述无水氯化铝的质量为四氟硼酸锂质量的0.2%~2%。A method for preparing lithium difluoroborate doped and coated SiO/C composite material according to claim 1, characterized in that: the mass of the anhydrous aluminum chloride is 0.2%~ of the mass of lithium tetrafluoroborate. 2%.
  7. 根据权利要求1所述的一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，其特征在于：所述反应的条件为：温度为0℃~20℃，时间为0.5~10h。A method for preparing lithium difluoroxaloborate doped and coated SiO/C composite material according to claim 1, characterized in that: the reaction conditions are: the temperature is 0°C~20°C, and the time is 0.5~ 10h.
  8. 根据权利要求1所述的一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的制备方法，其特征在于：所述静置结晶的条件为：温度为大于-40℃，且小于0℃，时间为0.5~10h。A method for preparing lithium difluoroxaloborate doped and coated SiO/C composite materials according to claim 1, characterized in that: the conditions for the static crystallization are: the temperature is greater than -40°C and less than 0 ℃, time is 0.5~10h.
  9. 一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料，其特征在于：由权利要求1~8任一项所述的制备方法得到。A lithium difluoroxalate borate doped and coated SiO/C composite material, which is characterized in that it is obtained by the preparation method described in any one of claims 1 to 8.
  10. 权利要求9所述的一种二氟草酸硼酸锂掺杂包覆SiO/C复合材料的应用，其特征在于：作为锂离子电池负极材料应用。The application of a lithium difluoroxaloborate doped and coated SiO/C composite material according to claim 9, characterized in that it is used as a negative electrode material for lithium ion batteries.
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