Sputtered Silicon-Coated Graphite Electrodes as High Cycling Stability and Improved Kinetics Anodes for Lithium Ion Batteries.

Amorphous Si thin films with different thicknesses were deposited on synthetic graphite electrodes by using a simple and scalable one-step physical vapor deposition (PVD) method. The specific capacities and rate capabilities of the produced electrodes were investigated. X-ray diffraction, scanning electron microscopy, Raman spectroscopy, profilometry, cyclic voltammetry, galvanostatic techniques, and in situ Raman spectroscopy were used to investigate their physicochemical and electrochemical properties. Our results demonstrated that the produced Si films covered the bare graphite electrodes completely and uniformly. Si-coated graphite, Si@G, with an optimal thickness of 1 μm exhibited good stability, with an initial discharge capacity of 628.7 mAhg, a capacity retention of 96.2%, and a columbic efficiency (CE) higher than 99% at C/3. A discharge capacity of 250 mAh g was attained at a high current rate of 3C, which was over 2.5 times that of a bare graphite electrode, thanks to the high activated surface area (1.5 times that of pristine graphite) and reduced resistance during cycling.