Preparation, Characterization and Electrochemical Performance of Silicon Coated Natural Graphite as Anode for Lithium Ion Batteries

摘要

The natural graphite (NG) coated silica is prepared by the hydrolysis of tetraethyl silicate, then reducedo by magnesium at 700 C to form NG-Si composite with 10 wt.% silicon. The result of scanningelectron microscopy shows that the silicon is coated on the surface of natural graphite with aninhomogeneous distribution. The result of X-ray diffraction shows that the silicon is formed withresidual SiO and SiO2, and the particle size calculated from the Si(111) face is 39.2 nm. The composite-1 with PVdF as binder shows a reversible capacity of 458.8 mAh g with good capacity retention of85.4% after 50 cycles. The replacement of PVdF by SBR-CMC further improves the capacity retentionto 90.7% and the cell charged at 1 C and 2 C rates shows little difference to that charged at 0.1 C. Thesmall particle size is the reason of high capacity retention and the naked NG surface supplies the routefor the fast electron transfer. The results present that the NG-Si composite prepared by hydrolysis oftetraethyl silicate on NG, then reduced by magnesium is a simple, low price and easily scale-upmethod improving the electrochemical performance of silicon anode.