A low temperature molten salt process for aluminothermic reduction of silicon oxides to crystalline Si for Li-ion batteries

Abstract

A low temperature molten salt process is developed to prepare crystalline Si nanoparticles through the reduction of micro-sized high silicon zeolite by metallic Al (or Mg) in molten AlCl₃. The reaction can be initiated at 200 °C, and the yield is about 40%. As the reaction temperature increases to 250 °C, the yield can reach about 75%. When the prepared Si was used as an anode for Li-ion batteries, reversible capacities of 2663 mA h g⁻¹ at 0.5 A g⁻¹ after 50 cycles and 870 mA h g⁻¹ at 3 A g⁻¹ after 1000 cycles can be obtained. Similarly, this synthetic strategy is employed to synthesize Si nanoparticles starting from various abundant raw materials including SiO₂ powder, kieselguhr, fiberglass, and even the natural mineral of albite.