Reduction of SiO2 by Metallic Li with a By-Product Soluble in Recyclable Molten LiCl Salt

As the production of Si via the carbothermic reduction of SiO2 by coke requires high temperatures and generates CO2, lower-temperature CO2-neutral reduction methods are highly sought after. However, the currently available alternatives exhibit important drawbacks such as the need for treatment with strong acids to separate Si from the mixture of solid reduction products. Herein, we studied the CO2-neutral reduction of amorphous SiO2 by Li metal in molten LiCl at 650 °C. The micro-/nanoparticulate crystalline Si was obtained by controlling the amount of metallic Li in molten LiCl. Since Li2O produced as a by-product is well soluble in LiCl, the micro-/nanoparticulate crystalline Si could be easily separated from the product mixture (Si-Li2O-LiCl) by treatment with water. Furthermore, LiCl could be recovered and recycled. This methodology was successfully applied to the reduction of sea sand and soil as SiO2 sources. The obtained Si was evaluated as an anode material for Li-ion batteries, offering the advantages of good cycling performance.