Plasma-prepared Silicon Nanomaterials With Optical And Electrochemical Properties

With the advancement of society,Si semiconductor materials have also developed rapidly.At present,the traditional non-renewable energy sources such as coal,oil and natural gas are gradually decreasing,and accompanied by environmental pollution,all countries have begun to vigorously develop green energy and renewable energy.In addition,the position of semiconductor silicon materials in the fields of microelectronics and optoelectronics is also important.Therefore,there is a higher demand for increasing research on lithium-ion batteries and photovoltaic materials.At present,although the commercial graphite material of lithium ion battery anode is stable,its lower theoretical specific capacity(372 mAh/g)is difficult to meet the needs of society,so Si material with higher theoretical capacity(4200 mAh/g)is obtained.People have a lot of attention.However,the Si material is accompanied by a huge volume expansion in the cycle work,which restricts its commercial application.In addition,the Si semiconductor material belongs to the indirect band gap,and its own luminous efficiency is extremely low,and it is also difficult to directly apply it to the field of optoelectronics.In order to solve the above problems,this thesis explores the optical properties of nano-silicon materials prepared by high-frequency thermal plasma and the application of lithium-ion battery anodes.Its main contents are as follows:1.Silicon nanomaterial with size of 40-100 nm is prepared by a high-frequency frequency thermal plasma method.The optical properties of the different collection points of the reactor,corundum,bag and cylinder bottom were analyzed by reducing the material's own dimensions and adjusting the indirect energy band of the Si itself.The bandgap of expanded Si is broadened to a wider range,and they are found to exhibit different properties in the ultraviolet,visible,and infrared bands.Further exploration of photoluminescence revealed that the material was emitted as a Raman spectrum.2.The bean-structured "Coated" Si/C composite nanomaterial was prepared by high energy ball milling.As a negative electrode material of a lithium ion battery,it exhibits excellent electrochemical performance.The electrode materials exhibited specific capacities of 1162.2 mAh/g and 920.6 mAh/g at a current density of 0.1 C and a current density at 0.2 C,respectively.In particular,the charge-discharge specific capacity of the Si/C composite material can be maintained at 743.4 mAh/g under the condition of circulating more than 200 cycles at a current density of 0.1 C.3.Commercial graphite is introduced into the above-mentioned obtained Si/C composite material for regulation by means of secondary ball milling.The "sand-flow"Silicon nanomaterial with better electrochemical performance was prepared.The electrode material exhibited a specific capacity of 806.9 mAh/g at a current density of 0.1 C.And under the condition of more than 150 cycles,the charge-discharge specific capacity of the Si/C composite material can still maintain a highly stable and slightly rising trend,and the Coulomb efficiency is always above 95%in the whole cycle.It exhibits more excellent stability.