Research On The Preparation Of Nano-silicon Oxide By Thermal Plasma Method

Nanoscale silicon suboxide?nano-SiO_x,x<2?has good chemical properties,and has a wide range of applications in fields of coating,fine ceramics preparation,and lithium ion battery anode materials.In application as anode material of lithium-ion battery,nano-SiO_xplay a significant role in increasing capacity of lithium-ion batteries.And because of its long cycle life and low cost,it has extremely promising applications.consequently,huge yield gap become an issue.Traditional methods used can prepare nano-SiO_xpowders with different particle sizes,it has the advantages of simple preparation method,easy operation and low cost.but they encounter some problems,such as low yield,uneven particle size distribution,and serious particle agglomeration.Thermal plasma method is an effective one to overcome these problems.Plasma approach,as an important nanomaterial preparation technology,effectively changes particle size of materials to play a role in nanometerization.Thermal plasma method is used to prepare nano-SiO_xpowder in this thesis.Preparation process was explored,the optimum process parameters were selected,and the experimental data would contribute to further experiment of preparing nano-SiO_xpowder.The research content and conclusion are as follows:1.This project used metallurgical grade SiO,diamond wire-cut silicon powder,and silicon dioxide powder as raw materials.The SiO powder were gasified and rapidly condensed by high temperature,energy concentration,and high-speed argon plasma flow to form nano-sized SiO_xparticles.Products were collected and subjected to physical and micromorphological characterization and electrochemical performance testing.2.After thermal plasma treatment particle size of raw SiO was significantly reduced,and particle size distribution was more uniform with increase of plasma power within a certain range.Prepared nano-SiO_xare nearly spherical particles with smooth surface and amorphous state,which reflects mechanism of uniform nucleation of nano-powder prepared by thermal plasma method.Increasing flow rate of the main gas was not conducive to reduce agglomeration of particles,and particle size increased with increasing flow rate within a certain range of main gas flow rate.And specific surface area of prepared powder decreased with increasing flow rate of main gas.Under certain conditions,increasing cooling rate was beneficial to suppress occurrence of disproportionation reactions.3.Nano-SiO_x was prepared using thermal plasma method and its application as anode material of lithium ion battery was also investigated.Nano-SiO_xderived from different thermal plasma power,including 13.2 k W,14.3 k W,and 15.4 k W were examined as anode material of lithium-ion battery.Corresponding first discharge capacity was 1732 m Ah·g^-1,1771 m Ah·g^-1,1924 m Ah·g^-1,and its capacity was maintained at 313 m Ah·g^-1,316 m Ah·g^-1,395 m Ah·g^-1after 50 cycles.While initial discharge capacity of original SiO particles was about 1291 m Ah·g^-1,and maintained at 75 m Ah·g^-1after 50 cycles.Lithium-ion battery with as-prepared nano-SiO_xanode exhibited improved electrochemical performance.