Preparation Of Spherical Nano Silicon Powder By Thermal Plasma Method

Nano-silicon powder is widely used in many fields,such as solar photovoltaic,light-emitting diode,biomedical and so on.At the same time,due to the high lithium storage capacity and good safety of silicon,nano-silicon powder has great potential in the field of lithium battery anode materials,followed by a huge production gap.The traditional preparation processes have many problems,such as high energy consumption,low efficiency and unmanageable product quality.In this paper,industrial silicon powder was used as raw material to prepare nano-silicon powder by thermal plasma method.The raw materials and preparation process of nano-silicon powder were further explored,the experimental data of the expanded experiment of preparing nano-silicon powder were obtained..The technological route of this experiment is as follows: firstly,industrial silicon powder were milled to micron level.Then,they were feeded into DC plasma furnace,and products are collected in the furnace collection area.After dissolved it in absolute ethanol,the nano-silicon powder with high purity was obtained by ultrasonic vibration,static separation and vacuum evaporation.Finally,the nano-silicon/carbon composites with good electrochemical properties were obtained by PECVD method.X-ray powder diffraction(XRD),transmission electron microscopy(TEM),selective electron diffraction(SAED),scanning transmission electron microscopy(STEM),specific surface area tester(BET)and Xinwei battery testing system were used to study the phase composition,micro-morphology,basic physical properties and electrochemical properties of nano-silicon powder.In this paper,the effects of various process parameters on the morphology,particle size and oxidation degree of nano-silica powder prepared by thermal plasma method were systematically investigated.The effects of various process parameters on nano-silica powder were summarized.The electrochemical performance of the nano-silica powder was tested.It was found that when sodium alginate was used as binder,the active material,conductive agent and binder were mixed in the proportion of 6:2:2 by mass ratio,the first discharge capacity of the assembled silicon-basednegative material for lithium battery could achieved 2325 mAh/g at the current density of 0.2 C.After 50 cycles,the capacity maintained at 850 mAh/g.Carbon film was deposited on the surface of nano-silicon powder by PECVD method,and silicon-carbon composite material was prepared.The modified nano-silicon-carbon powder was used as active material.Cyclic charge-discharge test was carried out at current density of 0.2 C.The first discharge capacity of the modified nano-silicon powder reached 2663mAh/g.After 50 cycles,the capacity maintained at 925 mAh/g.The first discharge specific capacity and cycle stability of the modified nano-silicon powder were somewhat improved.