Preparation of Nanocrystalline Silicon from SiCl 4 at 200 °C in Molten Salt for High‐Performance Anodes for Lithium Ion Batteries

Crystalline Si nanoparticles are prepared by reduction of SiCl 4 with metallic magnesium in the molten salt of AlCl 3 at 200 °C in an autoclave. AlCl 3 not only acts as molten salt, but also participates in the reaction. The related experiments confirm that metallic Mg reduces AlCl 3 to create nascent Al which could immediately reduce SiCl 4 to Si, and the by‐product MgCl 2 would combine with AlCl 3 forming complex of MgAl 2 Cl 8 . As anode for rechargeable lithium ion batteries, the as‐prepared Si delivers the reversible capacity of 3083 mAh g −1 at 1.2 A g −1 after 50 cycles, and 1180 mAh g −1 at 3 A g −1 over 500 cycles.