Catalyst-free synthesis of Si-SiO_x core-shell nanowire anodes for high-rate and high-capacity lithium-ion batteries

Si-SiO_x core-shell nanowires (NWs) ranging from 10 to 30 nm in diameter are prepared by a simple evaporation of silicon monoxide and control of substrate temperatures without any catalyst. The Si-SiO_x NWs grown at 735 and 955 °C are strongly anchored to the Cu current collector by forming copper silicide at the interface between Si and Cu, and subsequently used as anodes in lithium-ion batteries, in which no binder or conducting materials are used. The Si-SiO_x NWs anodes show excellent electrochemical performances in terms of capacity retention and rate capability. In particular, the Si-SiO_x NW anode grown at 955 °C shows a reversible capacity of ∼1000 mAh g^-1 even at a high-rate of 50 C. This catalyst-free synthetic route of Si-SiO_x NWs that are strongly anchored to the Cu current collector opens up an effective process for fabricating other high-capacity anodes in lithium-ion batteries (LIBs).