Preparation of Nanocrystalline Silicon from SiCl4 at 200°C in Molten Salt for High-Performance Anodes for Lithium Ion Batteries

Crystalline Si nanoparticles are prepared by reduction of SiCl4 with metallic magnesium in the molten salt of AlCl3 at 200 degrees C in an autoclave. AlCl3 not only acts as molten salt, but also participates in the reaction. The related experiments confirm that metallic Mg reduces AlCl3 to create nascent Al which could immediately reduce SiCl4 to Si, and the by-product MgCl2 would combine with AlCl3 forming complex of MgAl2Cl8. As anode for rechargeable lithium ion batteries, the as-prepared Si delivers the reversible capacity of 3083 mAhg(-1) at 1.2 Ag-1 after 50 cycles, and 1180 mAhg(-1) at 3 Ag-1 over 500 cycles.