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

Abstract

Crystalline Si nanoparticles are prepared by reduction of SiCl₄ with metallic magnesium in the molten salt of AlCl₃ at 200 °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 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.