Study Of Silicon/carbon Composite Synthesized By Chemical Vapor Deposition As Anode For Lithium-ion Battery

Lithium ion batteries(LIBs)as environmentally friendly energy conversion and storage systems have been widely applicated in portable electronic devices.In response to the growing energy requirement,the research efforts are mainly focused on searching for materials with higher energy density and prolonged cycle life.Silicon owns appreciable capacity(ten times higher than that of commercial graphite anode)up to 3572 mAh.g-1,low work potential and natural abundance which make silicon become the most promising anode candidate of new generation LIBs with high performance.However,the poor conductivity and huge volume strain during cycling processes limited its practical applications.Carbon has excellent mechanical and electrical properties,thus fabricating Si/C composites is one of the most efficient methods to improve the electrochemical performance of silicon.In this paper,embedded porous Si/C composites were constructed by means of chemical vapor deposition(CVD)process,to improve the electrochemical performance of silicon.Accordingly,the following two aspects were mainly studied:(1)Carbon paper,melamine formaldehyde(MF)foam and Cu-CuO were selected as three-dimensional(3D)porous matrices for silicon deposition.We aim to find the suitable skeleton for porous Si/C composites through comparing the electrochemical performance of all selected samples,which can help confirming the design idea of fabricating 3D porous Si/C composites.(2)The binder free TiO2-nanowires(NWs)-C/Si/C 3D network composite has been prepared by chemical vapor deposition(CVD)and facile carbonization process.In this composite,the intertwined TiO2-NWs serves as a buffer matrix to alleviate the volume strain of silicon during cycling processes,while the dual protective carbon layers enhance the conductivity of TiO2-NWs and prevent Si from peeling off the substrate.The as prepared TiO2-NWs-C/Si/C anode shows great cycling performance with a reversible capacity of 1850 mAh g-1 at 0.5 A g-1.At the higher current density of 2 A g-1,it exhibits excellent cycle stability with a capacity retention of 85.7%up to 100 cycles.