Alumina coated nano silicon synthesized by aluminothermic reduction as anodes for lithium ion batteries

Alumina (Al 2 O[Formula: see text] coated nano silicon was synthesized by aluminothermic reduction for the first time. It was realized by preoxidation of the nano silicon followed by a aluminothermic reduction that transformed the surface silicon oxide into Al 2 O 3 . The thickness of Al 2 O 3 can be controlled by regulating the preoxidized temperature and the processing time. The nano silicon coated with 2–4[Formula: see text]nm Al 2 O 3 showed a more stable cycling performance and a higher coulombic efficiency than the uncoated nano silicon. It is believed that the improved electrochemical performance was benefited from the Al 2 O 3 coating, which could hinder the side chemical reactions during the cycling process. This work provides an alternative method for surface coating on nanomaterials by safe and flexible solid state chemical reaction.