Uniform Carbon Coating on Silicon Nanoparticles by Dynamic CVD Process for Electrochemical Lithium Storage

Abstract

A uniform carbon layer was coated on Si nanoparticles by the dynamic chemical vapor deposition (CVD) process with toluene as the carbon source. The carbon layer thickness could easily be adjusted by controlling the preparation conditions. Samples selected from different positions of the reaction tube showed a small deviation in carbon content. As an anode material for a lithium-ion battery, the resulting Si@C composites exhibited better cycle reversibility and rate capability than pristine Si. The Si@C-2 sample (carbon layer thickness ≈ 12 nm) delivered a relatively stable specific capacity of ca. 1600 mA h g–1 at 0.3 A g–1 for 70 cycles. Its capacity remained at 750 mA h g–1 at 5 A g–1, compared with 240 mA h g–1 for pristine Si. Acetylene as a carbon source can also lead to superior cycle stability. This reformative CVD process provides an avenue for the large-scale production of uniform carbon coating materials used for batteries and other devices.