Nanoporous silicon prepared through air-oxidation demagnesiation of Mg2Si and properties of its lithium ion batteries.

Nanoporous silicon has been prepared through the air-oxidation demagnesiation of Mg2Si at 600 °C for 10 hours (Mg2Si + O2 → Si + MgO), followed by HCl washing. Mg2Si was prepared from 200 mesh commercial Si at 500 °C for 5 h in an autoclave. The as-prepared Si exhibits a reversible capacity of 1000 mA h g(-1) at 36 A g(-1) and ∼1200 mA h g(-1) at 1.8 A g(-1) over 400 cycles.