WO2021056981A1 - 一种锂电池硅基复合负极材料的制备方法 - Google Patents

一种锂电池硅基复合负极材料的制备方法 Download PDF

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WO2021056981A1
WO2021056981A1 PCT/CN2020/079406 CN2020079406W WO2021056981A1 WO 2021056981 A1 WO2021056981 A1 WO 2021056981A1 CN 2020079406 W CN2020079406 W CN 2020079406W WO 2021056981 A1 WO2021056981 A1 WO 2021056981A1
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raw material
silicon
preparation
based composite
magnesium
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French (fr)
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郭玉国
黄林波
徐泉
殷雅侠
岳风树
姚钧
赵岸光
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中国科学院化学研究所
北京壹金新能源科技有限公司
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Priority to US17/753,303 priority Critical patent/US11637273B2/en
Publication of WO2021056981A1 publication Critical patent/WO2021056981A1/zh

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Definitions

  • the invention belongs to the technical field of batteries, and specifically relates to a method for preparing a silicon-based composite negative electrode material for a lithium battery.
  • Lithium-ion batteries have been widely used in consumer electronics, power tools, medical electronics and other fields due to their high specific capacity, high energy density and power density, no self-discharge, and green environmental protection.
  • the current negative electrode materials in commercial lithium-ion batteries are mainly low-capacity graphite materials with a theoretical capacity of only 372mAh/g, which limits the application of lithium-ion batteries in the fields of electric vehicles and large-scale energy storage. Therefore, the development of high-capacity anode materials for lithium-ion batteries is the key to solving the energy problems in today's society.
  • silicon-based anode materials have attracted wide attention because of their ultra-high lithium storage capacity (4200mAh/g) and low voltage platform, which are ideal next-generation anode materials for lithium-ion batteries.
  • silicon-based materials have many problems in the process of charging and discharging lithium ions: 1. Huge volume change: the volume of silicon materials will expand to 300% of the original volume during the process of lithium ion insertion. It also shrinks sharply, which causes the active material particles to break and the electrode sheet to fall off and pulverize, and the cycle life is sharply reduced; 2. Large irreversible capacity, low Coulomb efficiency: The first coulombic efficiency of silicon-based materials is low, especially for silicon oxide materials.
  • Patent CN 108448096 A discloses a high-capacity core-shell amorphous carbon-based composite material.
  • This invention uses polyhedral cage oligomeric silsesquioxane as the precursor of the carbon-silicon coating layer, and further Coating conductive carbon or thermal cracking carbon to prepare a core-shell type amorphous carbon-based composite material.
  • the core-shell type composite material effectively alleviates the volume expansion during the cycle process and has excellent cycle performance.
  • the core-shell type structure cannot maintain the existing morphology during the preparation of the electrode sheet, and the new shape will be exposed after the pole piece rolling.
  • the SEI grows continuously on the interface, causing degradation of battery performance.
  • Patent CN201110149645 discloses a method for preparing porous silicon using magnesium thermal reduction.
  • the invention uses a large amount of magnesium to reduce silicon oxide to silicon, thereby solving the problem of oxygen in silicon oxide consuming lithium ions.
  • this method destroys The original silicon-oxygen structure of silicon oxide cannot effectively buffer the volume expansion, which makes the cycle performance of the battery poor.
  • SiOx in the silicon-based material is converted into silicate form as a buffer point.
  • silicate is used as an inactive material Expansion will occur, thereby reducing the expansion rate of the silicon-based negative electrode material.
  • CN106356508A discloses a silicon-based negative electrode material, including silicon and silicon oxide (SiOx, 0 ⁇ x ⁇ 2). The SiO vapor and the reducing substance vapor are reacted in a gas phase, and condensed to obtain the composite as a silicon-based anode material.
  • CN106537659A discloses a negative electrode active material, which heats silicon oxide powder and metal M at a high temperature to form silicate and distribute it in the silicon-based composite material to buffer the expansion.
  • CN105849953A discloses a nano-silicon/graphene composite negative electrode material,
  • the silicon oxide itself is uniformly distributed with silicon atoms and oxygen atoms, but due to the problem of processing temperature, silicon atoms will agglomerate to form silicon crystal regions.
  • the more crystal regions, the more serious the agglomeration of silicon, and the silicon in the crystal regions The volume expansion during charging and discharging is obviously larger than that of the uniformly dispersed silicon oxide, resulting in the battery's cycle stability not being uniformly dispersed, so the material should be made as amorphous as possible. Therefore, it is of extremely important and practical significance to develop a silicon-based composite material that can reduce the proportion of crystalline regions of the negative electrode material during the preparation process.
  • the purpose of the present invention is to solve the problems of low coulombic efficiency and poor cycle performance of the existing silicon-based composite materials, and to provide a method for preparing silicon-based composite anode materials for lithium batteries to improve the cycle life of current lithium-ion battery anode materials And energy density.
  • the invention prepares a silicon-based composite negative electrode material for lithium ion batteries by using a method of in-situ doping alkali metals, alkaline earth metal elements or elements of the third main group.
  • the inactive components mainly oxygen in silicon oxide
  • the product silicate can buffer the volume expansion during the lithium insertion process.
  • the inventor discovered that the use of a part of the alloy to replace elemental metals or metal oxides/peroxides results in a small proportion of the crystal regions of the silicon-based composite material, which is beneficial to increase the cycle life and energy density of the negative electrode material, thereby greatly improving The first lap Coulomb efficiency and cycle performance of the silicon oxide material make it have a very broad application prospect.
  • the present invention provides a method for preparing a silicon-based composite negative electrode material for a lithium battery, which includes the following steps:
  • the raw material A in step (1) is one or a combination of two or more of silicon powder, silicon oxide powder, and silicon dioxide powder;
  • the raw material B is selected from the group consisting of alkali metals, alkaline earth metals, and third main components. At least one of the simple substance of group elements and their oxides and alloys, provided that the alloy occupies more than 20 wt% of the raw material B.
  • the high-temperature treatment in step (2) is to first heat to 1000-1600°C, with a holding time of 10-16h; then gradually lower the temperature by 900-1200°C, and hold the time for 6-10h.
  • the basic elements of the alkali metals, alkaline earth metals and the third main group are selected from lithium, sodium, magnesium, calcium, and aluminum; their oxides/peroxides are selected from lithium oxide, lithium peroxide, sodium oxide, sodium peroxide, At least one of magnesium oxide, magnesium peroxide, calcium oxide, calcium peroxide, potassium oxide, potassium peroxide, and aluminum oxide, and the alloy is selected from the group consisting of magnesium lithium alloy, magnesium sodium alloy, magnesium calcium alloy, magnesium aluminum alloy, and magnesium manganese alloy .
  • the alloy accounts for more than 30 wt% of the raw material B, and more preferably, the alloy accounts for more than 50 wt% of the raw material B.
  • the uniform mixing in step (1) can be processed by ball milling and liquid phase mixing followed by spray drying, or by solid phase physical mixing such as high-speed mixers, VC mixers, etc.;
  • the non-oxidizing atmosphere includes nitrogen, argon, and helium.
  • the drying treatment is preferably a vacuum drying treatment; the drying treatment temperature is 30-100° C., and the drying treatment time is 2-8 hours.
  • step (2) the vacuum degree of the vacuum furnace is 1-100 Pa, and the condensation deposition temperature is 100-200°C.
  • the vacuum heating in step (2) is realized by a vacuum furnace with a deposition system; the vacuum furnace with a deposition system has one or two or more heating chambers.
  • raw material A and raw material B are heated in the heating chamber to generate steam to react; when the vacuum furnace has two or more heating chambers, place raw material A and raw material B in different heating chambers. body;
  • the heating temperature of the heating chamber where the raw material A is placed is 1200-1600°C; the heating temperature of the heating chamber where the raw material B is placed is 1000-1200°C;
  • the gas path through which the gas from the heating chamber enters the deposition system is adjustable.
  • the gas flow into the deposition system is that the volume flow ratio of the steam of the raw material A and the vapor of the raw material B is 100:1-20, more preferably 100:5 -15.
  • Controlling the steam of raw material A and raw material B within the above numerical range can consume more inactive components in the silicon oxide, improve the first coulombic efficiency of the material, and at the same time ensure the higher capacity of the silicon oxide material. If it is lower than the above numerical range, the effect of improving the first coulombic efficiency is unclear. If it is higher than the above numerical range, too much inactive components are introduced, which seriously reduces the specific capacity of the composite material.
  • the appropriate particle size in step (3) is to crush the material to a median particle size of 1-20 ⁇ m, preferably 2-10 ⁇ m.
  • the carbon coating is liquid coating, solid phase coating or chemical vapor deposition coating, and an amorphous carbon coating layer is formed on the surface of the silicon substrate.
  • the carbon material accounts for 5%-10wt% of the silicon-based composite material.
  • the equipment used for crushing in step (3) includes one or more combinations of counter-roll, jaw crushing, jet milling, mechanical crushing, ball milling, and sand milling, preferably one of counter-rolling, jaw crushing, jet milling, and ball milling Or multiple combinations;
  • the suitable particle size refers to pulverizing the material to a median particle size of 1-20 ⁇ m, preferably 2-10 ⁇ m;
  • the carbon coating is liquid-phase coating, solid-phase coating or chemical vapor deposition coating;
  • the equipment used for the liquid-phase coating is a ball mill or a sand mill; and the coating agent is coal pitch, petroleum pitch, needle-shaped One or more of coke or petroleum coke; after the liquid phase is uniformly mixed, the solvent is removed by spray drying or vacuum drying and sintered at a high temperature;
  • the sintering temperature of the liquid phase coating is 400-800°C, preferably 500-700°C
  • the sintering time of the liquid phase coating is 1-3h, preferably 1.5-2.5h;
  • the equipment used for the solid phase coating is a solid phase coating machine;
  • the coating agent is coal tar pitch, petroleum pitch, needle coke or One or more of petroleum coke,
  • the temperature of solid phase coating is 400-800°C, preferably 500-700°C;
  • the time of solid phase coating is 1-3h, preferably 1.5-2.5h;
  • the chemical The gas source of the vapor deposition method is one or
  • the thickness of the carbon-coated coating layer is 1-30 nm, more preferably 5-20 nm.
  • the invention also provides a silicon-based composite negative electrode material for a lithium battery prepared by the above-mentioned preparation method.
  • the preparation method of the silicon-based composite negative electrode material provided by the present invention has the following advantages:
  • the inactive components that can consume lithium ions are pre-consumed by the doped alkali metal elements, alkaline earth metal elements and the third main group elements, which effectively improves the composite material
  • the first Coulombic efficiency; the product of the reaction of alkali metal elements, alkaline earth metal elements and the third main group element with inactive components, silicate can buffer the volume expansion generated during the lithium intercalation process, thereby effectively improving the cycle performance of the composite material; Uniform carbon coating is also conducive to improving the conductivity of the material and improving the rate performance of the composite material.
  • the inventor unexpectedly discovered that a certain amount of alkali metals, alkaline earth metals, and alloys of the elementary elements of the third main group are added to the reducing substances of the raw material B that can react with SiO x to produce silicate, especially
  • the alloy containing magnesium can effectively reduce the proportion of crystal regions in the silicon-based composite material obtained by condensation deposition, thereby greatly improving the first-loop Coulomb efficiency and cycle performance of the silicon oxide material.
  • the present invention also optimizes and screens the preparation process conditions, in particular, the vacuum furnace heat treatment is divided into heat preservation heat treatment at different temperatures in the heating stage and the cooling stage, and in a preferred embodiment, the raw material A and the raw material B is placed in different heating chambers for heating, and the flow rate ratio of the steam generated by raw material A and raw material B in the deposition zone is adjusted, so that the obtained silicon-based composite material is used as a lithium-ion battery anode material, and its performance is further improved.
  • the preparation method provided by the present invention also has the advantages of simple method, cheap and readily available raw materials, suitable for large-scale production, and high degree of practicality.
  • FIG. 1 is an X-ray diffraction spectrum of the silicon-based composite negative electrode material prepared in Example 1.
  • FIG. 2 is an X-ray diffraction spectrum of the silicon-based composite negative electrode material prepared in Comparative Example 1.
  • FIG. 3 is a transmission electron micrograph of the silicon-based composite negative electrode material prepared in Example 1.
  • FIG. 4 is a transmission electron microscope photograph of the silicon-based composite negative electrode material prepared in Comparative Example 1.
  • FIG. 4 is a transmission electron microscope photograph of the silicon-based composite negative electrode material prepared in Comparative Example 1.
  • Fig. 5 is a scanning electron micrograph of the silicon-based composite negative electrode material prepared in Example 1 of the present invention.
  • Example 6 is a charge-discharge curve at 0.2C when the silicon-based composite negative electrode material prepared in Example 1 of the present invention is used as the negative electrode of a lithium ion battery.
  • FIG. 7 is a cycle performance curve at 0.2C when the silicon-based composite negative electrode material prepared in Example 1 of the present invention is used as the negative electrode of a lithium ion battery.
  • FIG. 8 is a rate performance curve of the silicon-based composite negative electrode material prepared in Example 1 of the present invention when used as the negative electrode of a lithium ion battery.
  • Example 9 is an electrochemical impedance curve of the silicon-based composite negative electrode material prepared in Example 1 of the present invention after being used as the negative electrode of a lithium ion battery for 200 cycles.
  • the obtained deposition material is crushed to particles with a median diameter of about 5 ⁇ m through airflow, and then added to a CVD vapor deposition furnace for carbon coating treatment, and acetylene gas is introduced at a mass flow rate of 600 sccm, and deposited at 750 °C 3h, put the coated material under nitrogen protection, and heat up to 5°C/min
  • a silicon-based composite negative electrode material with SiO x and silicate evenly distributed and carbon-coated is obtained.
  • the thickness of the carbon-coated coating layer is 10nm, and the carbon material accounts for the silicon-based composite material ⁇ 5.5wt%.
  • the operation is carried out in the same manner as in Example 1, except that the raw material B in step (1) is 0.6Kg of metallic magnesium powder and 0.4kg of magnesium-aluminum alloy.
  • the operation is carried out in the same manner as in Example 1, except that the raw material B in step (1) is 0.8Kg of magnesium metal powder and 0.2kg of magnesium-aluminum alloy.
  • the operation is carried out in the same manner as in Example 1, except that the raw material B in step (1) is 0.3Kg of magnesium metal powder and 0.7kg of magnesium-aluminum alloy.
  • step (2) the dried raw materials A and B are added to the heating chamber of a vacuum furnace with a condensation collection system and heated to 1300°C for 20 hours, and then heated at 50°C/ The cooling rate of h is lowered to 1100°C, and the temperature is kept for 10h.
  • step (2) the volume flow ratio of the raw material A steam and the raw material B steam entering the deposition system is 100:8.
  • step (2) the magnesium-aluminum alloy is replaced with magnesium-lithium
  • step (1) the raw material B was 1 kg of magnesium powder.
  • step (1) The operation was performed in the same manner as in Example 1, except that in step (1), the raw material B was a mixture of 0.681 kg of magnesium powder and 0.319 kg of aluminum powder.
  • Fig. 1 The X-ray diffraction peaks of the composite material were analyzed with an X-ray diffraction analyzer (XRD, Rigaku D/max 2500, Cu K ⁇ ).
  • Figure 1 is the XRD diffraction pattern of the silicon-based composite material prepared in Example 1
  • Figure 2 is the comparative example. 2 XRD diffraction pattern of the prepared silicon-based composite material, it can be seen that Fig. 1 has no obvious diffraction peaks, only amorphous bulging, which proves the amorphous form of the material; Fig.
  • FIG. 3 and FIG. 4 are transmission electron micrographs of the silicon-based composite materials of Example 1 and Comparative Example 2, respectively. As can be seen in Figure 3, the silicon-based composite material prepared in Example 1 has no obvious crystal regions, indicating that the silicon oxide in the entire material is amorphous; Figure 4 shows that there are many lattice fringes in the darker place.
  • the lattice fringe area corresponds to where there is crystalline silicon.
  • the proportion of crystalline area is large.
  • the volume expansion rate of crystalline silicon is much greater than that of amorphous silicon oxide. Therefore, materials with crystalline structure are more likely to be broken during charging and discharging, leading to The material capacity decays quickly and the cycle performance is poor.
  • Figure 5 is a scanning electron microscope photo of the silicon-based composite negative electrode material prepared in Example 1.
  • the composite material is bulky, with a dense surface
  • the particle size is uniform, and the particle size range is 1-8 ⁇ m.
  • the particle size of the composite material was measured with a Malvern laser particle size analyzer (Malvern, Mastersizer 3000), and the median particle size was 4.8 ⁇ m.
  • the electrochemical performance of the silicon-based composite negative electrode materials prepared in the examples of the present invention and the comparative examples were tested according to the following method: the prepared silicon-based composite negative electrode materials, carbon black and carboxymethyl cellulose (CMC) Styrene rubber (SBR) composite binder is mixed with a mass ratio of 80:10:10 to form a slurry (where the mass ratio of CMC and SBR is 1:1), and the slurry is evenly coated on the copper foil current collector , And dried in vacuum for 12 hours to make a working electrode; use lithium flake as the counter electrode, glass fiber membrane (purchased from Whatman, UK) as the diaphragm, 1 mol/L LiPF 6 (solvent is ethylene carbonate and ethylene carbonate with a volume ratio of 1:1) Dimethyl carbonate mixture) is used as the electrolyte, and 1% VC and 5% FEC are added to the electrolyte, and the button cell is assembled in a German Braun inert gas glove box under an argon atmosphere.
  • CMC carboxy
  • the battery assembled above was charged and discharged on a LAND charge and discharge tester.
  • the electrochemical analysis test was carried out on the silicon-based composite negative electrode material obtained in Example 1.
  • the charge-discharge interval was 0-2V
  • the compaction density was 1.3g/cm 3
  • the current density was 380mA/g (0.2C).
  • the capacity can reach 1541.3mAh/g
  • the first lap coulombic efficiency is 83.8%
  • the capacity retention rate after 200 laps is 83.3% (as shown in Figure 6 and Figure 7).
  • the rate test it is found that the composite material has a high current of 5C.
  • the silicon-based composite materials obtained in the examples of the present invention and the comparative examples were used as negative electrode materials to be assembled into button-type lithium batteries.
  • the electrochemical test results are listed in Table 1.
  • the preparation method of the present invention is simple and efficient, and the obtained silicon-based composite negative electrode material has a stable structure. It has high first coulombic efficiency and good cycle performance. The capacity retention rate of 200 cycles is above 80%. Excellent electrochemical performance.

Abstract

本发明提供了一种锂电池硅基复合负极材料的制备方法，其是将含有Si的原料A和能反应生成硅酸盐的还原性物质原料B在真空加热条件下形成蒸汽，反应后在沉积***中冷凝沉积，之后进行碳包覆得到硅基复合材料。发明人预料不到发现，在原料B中加入一定量合金，能够减少硅基复合材料中晶区的比例，进而提高了负极材料的首次库伦效率和循环稳定性。本发明提供的制备方法也具有方法简单、原料便宜易得、适宜大规模生产、实用化程度高等优点。

Description

一种锂电池硅基复合负极材料的制备方法 技术领域
本发明属于电池技术领域，具体涉及一种锂电池硅基复合负极材料的制备方法。
背景技术：
随着便携式电子产品、电动交通工具以及储能电站等领域的快速发展，人们对储能设备的能量密度、功率密度和循环寿命等性能指标的要求也越来越高。锂离子电池由于具有高比容量、高能量密度和功率密度、无自放电、绿色环保等优点，已经在消费电子、电动工具、医疗电子等领域获得了广泛应用。然而目前商业化锂离子电池中的负极材料主要是低容量的石墨类材料，其理论容量仅为372mAh/g，限制了锂离子电池在电动交通工具及规模储能等领域中的应用。因此，开发锂离子电池高容量负极材料是解决当今社会能源问题的关键。
在新型锂离子电池负极材料方面，硅基负极材料因具有超高的储锂容量(4200mAh/g)和较低的电压平台，是非常理想的下一代锂离子电池负极材料而受到广泛关注。然而，硅基材料在充放电脱嵌锂离子的过程中具有较多问题：1.巨大的体积变化：硅材料在锂离子嵌入过程中体积会膨胀至原来的300％，在脱出锂离子时体积又急剧收缩，从而造成活性材料颗粒破碎以及电极片脱落粉化，循环寿命急剧下降；2.不可逆容量大，库伦效率低：硅基材料的首次库伦效率较低，特别是氧化亚硅材料，由于含有能消耗锂离子的非活性组分，首次充放电过程中会产生大量的不可逆容量，从而使正极匹配困难，全电池效率低且循环寿命短；3.极低的电导率：硅本身为半导体，导电性能差，不利于电子的快速传递，从而影响硅基负极材料容量的正常发挥。
针对上述体积膨胀问题，专利CN 108448096 A公开了一种高容量核壳型无定形碳基复合材料，该发明采用多面体笼型低聚倍半硅氧烷作为碳硅包覆层的前驱体，进一步包覆导电碳或热裂解碳，制得核壳型无定形碳基复合材料。核壳型的复合材料有效缓解 了循环过程中的体积膨胀，具有优异的循环性能，然而核壳型的结构在电极片制备过程中不能保持既有形貌，经过极片辊压会暴露新的界面而不断生长SEI，造成电池性能衰减。
专利CN201110149645公开了一种利用镁热还原制备多孔硅的方法，该发明是用大量的镁将氧化亚硅还原为硅，从而解决氧化亚硅中的氧消耗锂离子的问题，然而该方法破坏了氧化亚硅原有的硅氧结构，不能有效缓冲体积膨胀，而使电池的循环性能较差。
现有技术中报道了很多为了解决硅基负极材料，采用了在硅基材料中将部分SiO x转化为硅酸盐形式作为缓冲点，在电池充放电过程中，硅酸盐作为非活性物质不会发生膨胀，进而减少了硅基负极材料的膨胀率。CN106356508A公开了一种硅基负极材料，包括硅、硅氧化物(SiOx，0＜x≤2)。使SiO蒸汽和还原物质蒸汽以气相形式反应，凝结得到所述复合物作为硅基负极材料。CN106537659A中公开了负极活性材料，其是在高温下加热氧化硅粉末和金属M，形成硅酸盐分布在硅基复合材料中起到缓冲膨胀的作用。CN105849953A公开了一种纳米硅/石墨烯复合负极材料，
氧化亚硅本身是硅原子和氧原子均匀分布的，但是由于处理温度的问题，硅原子会团聚在一起形成硅晶区，晶区越多则说明硅的团聚越严重，而晶区中的硅在充放电的时候的体积膨胀明显要比均匀分散的氧化亚硅的大，导致电池的循环稳定性没有均匀分散的好，所以材料要尽量做成无定形。因此，开发一种能够在制备过程中减少负极材料晶区比例的硅基复合材料，具有极为重要和实际的意义。
发明内容
本发明的目的在于解决现有硅基复合材料首圈库伦效率低和循环性能不佳的问题，提供了一种锂电池硅基复合负极材料的制备方法，提升当前锂离子电池负极材料的循环寿命和能量密度。
本发明使用原位掺杂碱金属、碱土金属元素或第三主族元素的方法制备出一种用于锂离子电池的硅基复合负极材料。与其他制备方法相比，本发明方法得到的硅基复合材 料中能与锂离子结合的非活性组分(主要是氧化亚硅中的氧)被掺入的还原性元素组分预先消耗，且其产物硅酸盐能缓冲嵌锂过程中产生的体积膨胀。发明人预料不到地发现，采用一部分合金替代金属单质或者金属氧化物/过氧化物，得到的硅基复合材料晶区比例小，有利于提高负极材料的循环寿命和能量密度，从而大幅度提升氧化亚硅材料的首圈库伦效率和循环性能，使其具有非常广阔的应用前景。
为实现上述发明目的，本发明提供了一种锂电池硅基复合负极材料的制备方法，包括如下步骤：
(1)将能在高温下产生SiO x(0<x≤2)蒸汽的原料A和能够与SiO x蒸汽反应生成硅酸盐的原料B在非氧化气氛下干燥处理；
(2)将上述干燥后的原料A和原料B在真空下加热处理变为蒸汽，之后将两者产生的蒸汽均匀混合后冷凝沉积；
(3)将上述沉积后的材料破碎至合适粒度后进行碳包覆，得到硅基复合负极材料。
其中，步骤(1)中所述原料A为硅粉、氧化亚硅粉末、二氧化硅粉末中的一种或两种以上的组合；所述原料B选自碱金属、碱土金属、第三主族元素单质以及它们的氧化物和合金中的至少一种，条件是合金占原料B的20wt％以上。
优选地，步骤(2)中所述高温处理是先加热至1000-1600℃，保温时间为10-16h；再逐渐降低温度900-1200℃，保温时间为6-10h。
所述碱金属、碱土金属、第三主族元素单质选自锂、钠、镁、钙、铝；它们的氧化物/过氧化物选自氧化锂、过氧化锂、氧化钠、过氧化钠、氧化镁、过氧化镁、氧化钙、过氧化钙、氧化钾、过氧化钾、氧化铝的至少一种，合金选自镁锂合金、镁钠合金、镁钙合金、镁铝合金、镁锰合金。
作为本发明的优选技术方案，所述合金占原料B的30wt％以上，更优选的，合金占原料B的50wt％以上。
步骤(1)中所述均匀混合可通过球磨液相混合后喷雾干燥处理，也可通过高速混料 机、VC混料机等固相物理混合；所述非氧化气氛包括氮气、氩气、氦气、氖气和氪气中的一种或多种组合；所述干燥处理优选为真空干燥处理；干燥处理温度为30-100℃，所述干燥处理时间为2-8h。
步骤(2)中所述真空炉的真空度为1-100Pa，所述冷凝沉积温度为100-200℃。
进一步优选的，步骤(2)中所述真空加热是通过具有沉积***的真空炉实现的；所述具有沉积***的真空炉具有一个或两个及以上的加热腔体。
当真空炉具有一个加热腔体，原料A和原料B在该加热腔体内加热产生蒸气进行反应；当真空炉具有两个及以上加热腔体，将原料A和原料B分别放置于不同的加热腔体；
优选地，放置原料A的加热腔的加热温度为1200-1600℃；放置原料B的加热腔的加热温度为1000-1200℃；
加热腔体的气体进入沉积***的气路口径可调，优选地，进入沉积***的气体流量为原料A的蒸汽和原料B的蒸气体积流量比为100:1-20，更优选为100：5-15。控制原料A的蒸汽和原料B的蒸汽在上述数值范围内，能较多的消耗氧化亚硅中的非活性组分，提升材料的首次库伦效率，同时也保证氧化亚硅材料较高的容量，若低于上述数值范围，则提升首次库伦效率的效果就不明想，若高于上述数值范围，则引入的非活性组分就过多，严重降低复合材料的比容量。
步骤(3)中所述合适粒度是将材料破碎至中值粒径为1-20μm，优选为2-10μm。
所述碳包覆为液相包覆、固相包覆或化学气相沉积包覆，在硅基表面形成无定形的碳包覆层。碳材料占硅基复合材料的5％-10wt％。
步骤(3)中破碎所用的设备包括对辊、鄂破、气流粉碎、机械粉碎、球磨、砂磨中的一种或多种组合，优选对辊、鄂破、气流粉碎、球磨中的一种或多种组合；所述合适粒度是指将材料粉碎至中值粒径为1-20μm，优选为2-10μm；
所述碳包覆为液相包覆、固相包覆或化学气相沉积包覆；所述的液相包覆所用设备 为球磨机或砂磨机；包覆剂为煤沥青、石油沥青、针状焦或石油焦中的一种或多种；液相均匀混合后采用喷雾干燥或者真空干燥的方法除去溶剂并高温烧结；液相包覆的烧结温度为400-800℃，优选为500-700℃；液相包覆的烧结时间为1-3h，优选为1.5-2.5h；所述的固相包覆所用设备为固相包覆机；包覆剂为煤沥青、石油沥青、针状焦或石油焦中的一种或多种，固相包覆的温度为400-800℃，优选为500-700℃；固相包覆的时间为1-3h，优选为1.5-2.5h；所述化学气相沉积法的气源为乙炔、甲烷、丙烷、丁烷、苯和甲苯中的一种或两种组合；化学气相沉积包覆的温度为600-1100℃，优选为700-1000℃；化学气相沉积法包覆时间为1-6h，优选为2-5h。
优选地，所述的碳包覆的包覆层厚度为1-30nm，更优选为5-20nm。
本发明还提供了上述制备方法制得的锂电池硅基复合负极材料。
与现有技术相比，本发明提供的硅基复合负极材料的制备方法优势在于：
一、含有硅的氧化物和硅酸盐的复合结构中能消耗锂离子的非活性组分被掺入的碱金属元素、碱土金属元素和第三主族元素预先消耗，有效的提升了复合材料的首次库伦效率；碱金属元素、碱土金属元素和第三主族元素与非活性组分反应的产物硅酸盐能缓冲嵌锂过程中产生的体积膨胀，从而有效提升复合材料的循环性能；表面均匀的碳包覆也有利于提升材料的导电性，提升复合材料的倍率性能。
二、发明人预料不到地发现，在能与SiO x反应产生硅酸盐的原料B的还原性物质中，加入一定量的碱金属、碱土金属、第三主族元素单质的合金，特别是含有镁的合金，能有效减少冷凝沉积得到的硅基复合材料中晶区的比例，从而大幅度提升氧化亚硅材料的首圈库伦效率和循环性能。
三、本发明还对制备的各工艺条件进行了优化和筛选，特别是将真空炉加热处理分为加热阶段和降温阶段的不同温度的保温热处理，以及在优选实施方案中，将原料A和原料B放置在不同的加热腔体中分别进行加热，以及调控在沉积区原料A和原料B产生的蒸气的流量比例，使得到的硅基复合材料作为锂离子电池负极材料，性能进一步 提升。
四、在与除此之外，本发明提供的制备方法也具有方法简单、原料便宜易得、适宜大规模生产、实用化程度高等优点。
附图说明
图1为实施例1制得的硅基复合负极材料的X射线衍射谱。
图2为对比例1制得的硅基复合负极材料的X射线衍射谱。
图3为实施例1制得的硅基复合负极材料的透射电镜照片。
图4为对比例1制得的硅基复合负极材料的透射电镜照片。
图5为本发明实施例1制得的硅基复合负极材料的扫描电子显微镜照片。
图6为本发明实施例1制得的硅基复合负极材料作为锂离子电池负极时，在0.2C下充放电曲线。
图7为本发明实施例1制得的硅基复合负极材料作为锂离子电池负极时，在0.2C下的循环性能曲线。
图8为本发明实施例1制得的硅基复合负极材料作为锂离子电池负极时的倍率性能曲线。
图9为本发明实施例1制得的硅基复合负极材料作为锂离子电池负极循环200圈后的电化学阻抗曲线。
具体实施方式
下面结合具体实施例对本发明作进一步说明，但本发明并不限于以下实施例。
下述实施例中所述实验方法，如无特殊说明，均为常规方法；所述试剂和材料，如无特殊说明，均可从商业途径获得。
实施例1
(1)将3Kg Si粉末与6Kg SiO 2粉末加入高速混料机中，在惰性气氛保护并用循环水冷却的条件下1000r/min搅拌混合30min，得到混合均匀的原料A，然后将原材料A 在氩气保护下50℃保温2h充分除去水分；同时将0.5Kg金属镁粉以及0.5kg镁铝合金(其中镁含量36.2wt％)在氩气保护下50℃保温2h充分除去水分，为原料B。
(2)将上述烘干后的原材料A加入具有冷凝收集***的真空炉的加热腔1中，将真空抽至1Pa以下开始加热，加热到1300℃保温20h，再以50℃/h的降温速率降温至1100℃，保温10h；同时将烘干后的原料B加入加热腔2中，之后将真空抽至1Pa以下开始加热，加热到1000℃保温20h，再以50℃/h的降温速率降温至900℃，保温10h。调控加热腔体1和加热腔体2进入沉积***的气路口径，使进入沉积***原料A蒸汽和原料B蒸气体积流量比为100:13，同时控制沉积区的温度维持在600℃左右，自然冷却至室温后得到块状的沉积材料；
(3)将得到的沉积材料经过气流粉碎破碎至中值粒径为5μm左右的颗粒，加入CVD气相沉积炉中进行碳包覆处理，以600sccm的质量流量通入乙炔气，在750℃下沉积3h，并将包覆后的材料置于氮气保护的条件下，以5℃/min的升温速度升温至
900℃保温1h，自然冷却后得到SiO x、硅酸盐均匀分布并且外层有碳包覆的硅基复合负极材料，其中碳包覆的包覆层厚度为10nm，碳材料占硅基复合材料的5.5wt％。
实施例2
按照实施例1相同的方法进行操作，不同在于步骤(1)中原料B为0.6Kg金属镁粉以及0.4kg镁铝合金。
实施例3
按照实施例1相同的方法进行操作，不同在于步骤(1)中原料B为0.8Kg金属镁粉以及0.2kg镁铝合金。
实施例4
按照实施例1相同的方法进行操作，不同在于步骤(1)中原料B为0.3Kg金属镁粉以及0.7kg镁铝合金。
实施例5
按照实施例1相同的方法进行操作，不同在于步骤(2)中，烘干后的原材料A和B都加入具有冷凝收集***的真空炉的加热腔加热到1300℃保温20h，再以50℃/h的降温速率降温至1100℃，保温10h。
实施例6
按照实施例1相同的方法进行操作，不同在于步骤(2)中，进入沉积***的原料A蒸汽和原料B蒸气体积流量比为100:8。
实施例7
按照实施例1相同的方法进行操作，不同在于步骤(2)中，将镁铝合金替换为镁锂
合金。对比例1
按照实施例1相同的方法进行操作，不同在于步骤(1)中，原料B为1kg镁粉。
对比例2
按照实施例1相同的方法进行操作，不同在于步骤(1)中，原料B为0.681kg镁粉和0.319kg铝粉的混合物。
应用例
1.对负极材料的表征
用X射线衍射分析仪(XRD，Rigaku D/max 2500，Cu Kα)分析复合材料的X射线衍射峰，图1是实施例1制得的硅基复合材料的XRD衍射图谱，图2是对比例2所制得硅基复合材料的XRD衍射图谱，可看出图1没有明显的衍射峰，只有无定形的鼓包，证明了材料的无定形态；图2存在明显的硅和硅酸盐的衍射峰，在28.4°,47.3°和56.1°处的衍射峰对应于硅的(111),(220),(311)晶面，在31.0°的衍射峰对应于硅酸盐的衍射峰。衍射峰的存在说明材料中形成了明显的晶区。另外图3和图4分别为实施例1和对比例2的硅基复合材料的透射电镜照片。图3可以看出，实施例1制得的硅基复合材料没有明显的晶区，说明整个材料中氧化亚硅均为无定形态；图4可以看到比较暗的地方存在很多晶格条纹，晶格条纹区就对应着此处有晶体硅，晶区比例较大，而晶 体硅体积膨胀率远大于无定形的氧化亚硅，所以具有晶体结构的材料在充放电过程中更容易破裂，导致材料容量的快速衰减，循环性能很差。
用扫描电镜(SEM，日本电子扫描电镜JEOL-6701F)分析复合材料的形貌，图5为实施例1所制得硅基复合负极材料的扫描电镜照片，该复合材料为块状，表面致密且粒度均匀，粒径范围为1～8μm。用马尔文激光粒度仪(Malvern,Mastersizer 3000)测量复合材料的粒度，其中值粒径为4.8μm。
2,硅基复合材料作为锂电池负极材料的性能测试
将本发明实施例和对比例制备所得硅基复合负极材料的电化学性能均按照下述方法进行测试：将制备得到的硅基复合负极材料、碳黑和羧甲基纤维素(CMC)与丁苯橡胶(SBR)复合粘结剂以质量比80:10:10混合配成浆料(其中CMC和SBR的质量比为1:1)，将该浆料均匀地涂敷到铜箔集流体上，并经真空干燥12h后制成工作电极；以锂薄片作为对电极，玻璃纤维膜(购自英国Whatman公司)作为隔膜，1mol/L LiPF 6(溶剂为体积比1:1的碳酸乙烯酯和碳酸二甲酯混合液)作为电解液，电解液中添加体积分数为1％的VC和5％的FEC，在氩气氛围的德国布劳恩惰性气体手套箱中组装成扣式电池。
将上述装配的电池在LAND充放电测试仪上进行充放电测试。
对实施例1所得硅基复合负极材料进行电化学分析测试，充放电区间为0～2V，压实密度为1.3g/cm 3，在电流密度为380mA/g(0.2C)下充放电，材料容量可达1541.3mAh/g，首圈库伦效率为83.8％，且循环200圈后容量保持率为83.3％(如图6和图7)，在倍率测试中发现，该复合材料在5C的高电流密度下仍具有1311.6mAh/g的充电比容量(如图8，从左到右五段分别对应0.2C,1C,2C,5C,0.2C倍率下)，是0.2C下的85.1％，证明本发明所得复合材料具有较高的容量和优异的循环性能。对循环200圈后的电池进行电化学阻抗谱的测试，发现其电荷转移电阻仅为98.5Ω(如图9)，表明该材料具有较长的循环寿命。
按照相同的方法，对本发明实施例和对比例所得硅基复合材料作为负极材料组装为扣式锂电池中，其电化学测试结果列于表1。
表1
Figure PCTCN2020079406-appb-000001
表中上角标a表示在0.2C条件下测试得到。
综上所述，本发明的制备方法简单高效，得到的硅基复合负极材料本身结构稳定，在具有高首次库伦效率的同时也具有很好的循环性能，200圈容量保持率在80％以上，电化学性能优异。
申请人声明，本发明通过上述实施例来说明本发明的详细工艺设备和工艺流程，但本发明并不局限于上述详细工艺设备和工艺流程，即不意味着本发明必须依赖上述详细工艺设备和工艺流程才能实施。所属技术领域的技术人员应该明了，对本发明的任何改进，对本发明产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本发明的保护范围和公开范围之内。

Claims (9)

  1. 一种锂电池硅基复合负极材料的制备方法，包括如下步骤：
    (1)将能在高温下产生SiO x(0<x≤2)蒸汽的原料A和能够与SiO x蒸汽反应生成硅酸盐的原料B在非氧化气氛下干燥处理；
    (2)将上述干燥后的原料A和原料B在真空下高温处理为蒸汽，之后将两者产生的蒸汽均匀混合后冷凝沉积；
    (3)将上述沉积后的材料破碎至合适粒度后进行碳包覆，得到硅基复合负极材料。
    其中，步骤(1)中所述原料A为硅粉、氧化亚硅粉末、二氧化硅粉末中的一种或两种及以上的组合；所述原料B选自碱金属、碱土金属、第三主族元素单质以及它们的氧化物和合金中的至少一种，条件是合金占原料B的20wt％以上。
  2. 如权利要求1所述的制备方法，其特征在于，步骤(2)中所述高温处理是先加热至1000-1600℃，保温时间为10-16h；再逐渐降低温度900-1200℃，保温时间为6-10h。3、如权利要求1所述的制备方法，其特征在于，所述碱金属、碱土金属、第三主族元素单质选自锂、钠、镁、钙、铝；它们的氧化物/过氧化物选自氧化锂、过氧化锂、氧化钠、过氧化钠、氧化镁、过氧化镁、氧化钙、过氧化钙、氧化钾、过氧化钾、氧化铝的至少一种，合金选自镁锂合金、镁钠合金、镁钙合金、镁铝合金、镁锰合金。
  3. 如权利要求1所述的制备方法，其特征在于，所述合金占原料B的30wt％以上，优选的，合金占原料B的50wt％以上。
  4. 如权利要求1所述的制备方法，其特征在于，步骤(2)中所述真空炉的真空度为1-100Pa，所述冷凝沉积温度为100-200℃。
  5. 如权利要求1所述的制备方法，其特征在于，步骤(2)中所述真空加热是通过具有沉积***的真空炉实现的；所述具有沉积***的真空炉具有一个或两个及以上的加热腔体；
    当真空炉具有一个加热腔体，原料A和原料B在该加热腔体内加热产生蒸气进行反应；当真空炉具有两个及以上加热腔体，将原料A和原料B分别放置于不同的加热腔体。
  6. 如权利要求6所述的制备方法，其特征在于，当真空炉具有两个以上加热腔体时，放置原料A的加热腔的加热温度为1200-1600℃；放置原料B的加热腔的加热温度为1000-1200℃。
  7. 如权利要求6或7所述的制备方法，其特征在于，加热腔体的气体进入沉积***的气路口径可调，进入沉积***的气体流量为原料A的蒸汽和原料B的蒸气体积流量比为100:1-20，更优选为100:5-15。
  8. 如权利要求8所述的制备方法，其特征在于，碳材料占硅基复合材料的5％-10wt％，所述的碳包覆的包覆层厚度为1-30nm，优选为5-20nm。
  9. 权利要求1-9任一项所述制备方法制备得到的硅基复合负极材料，其特征在于，其含有无定形氧化亚硅。
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* Cited by examiner, † Cited by third party
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CN116960312A (zh) * 2023-09-18 2023-10-27 北京壹金新能源科技有限公司 改性硅基负极材料及其制备方法
CN116960312B (zh) * 2023-09-18 2024-03-01 北京壹金新能源科技有限公司 改性硅基负极材料及其制备方法

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