Study On The Synthesis,Structure Characterization And Electrochemical Properties Of Si/C Anode Materials For Lithium-Ion Batteries

With the progress of science and technology and the development of society,the traditional fossil fuel energy consumption is serious,and the energy crisis is becoming more and more intense.Therefore,it is urgent to find clean and stable new energy.The advantages of lithium-ion battery,such as high energy density,long service life,large rate of charge and discharge,good chemical stability,high energy density and no memory effect,have become the optimal choice of new energy storage.Graphite is the most widely used anode material for commercial lithium-ion batteries,but its theoretical specific capacity is low,372 mAh g^-1,which is difficult to meet the needs of modern social development.Therefore,the focus of current research is to develop new cathode materials.This paper focuses on the preparation of silicon carbon anode materials:1.In the first work,silicon/silica electrode materials with different particle sizes were prepared by thermite reduction method.The reaction process was systematically studied by means of XRD,SEM,TEM and XPS etching.The reaction started from the surface of the material and proceeded layer by layer.When the reaction reached a certain degree,the spherical silica would dissociate into crushed particles and continue to react until the end of the reaction.Then we assembled the button cell and tested the electrochemical performance of Si/SiO₂with different particle sizes(0.2,1and 10 microns),and the electrochemical performance of Si/SiO₂with 1 micron was the best.The specific discharge capacity of the first cycle is up to 3158 mAh·g^-1,and after 100 cycles,the specific discharge capacity is still about 880 mAh·g^-1.2.The second job to the modification of Si nanoparticles,we prepared Si/SiO₂/C material precursor by microwave hydrothermal method at different temperatures(120?,140?,160?),transferred to the tube furnace under 250?in air atmosphere pre oxidation treatment 2 h,high temperature carbonization temperature to 850?at nitrogen condition to obtain the core-shell structure of Si/SiO₂/C material.The core-shell structure of Si/SiO₂/C materials discharge specific capacity of 1899mAh g^-1for the first time,after 100 times charging and discharging cycle capacity still remaining 1077mAh g^-1.3.The third job looking for a new kind of preparation technology can simplify the battery production process,we take the in-situ generation method to make the material directly to grow in the collection of fluid on the surface of electrode materials,generate the pole piece of electrode materials and the collection of fluid combining ability is very good.After 200 cycles of charging and discharging,there is no phenomenon of separation between the fluid collector and the material.A series of processes such as slurry and film mixing of the battery are removed.After the material is made,the battery is directly cut and installed,and good results have been achieved.The first specific discharge capacity is 2891mAh g^-1,and after 120 cycles,the capacity remains 1474mAh g^-1.