Mg₂Si promoted magnesio-mechanical reduction of silica into silicon nanoparticles for high-performance Li-ion batteries

In this study, we report a scalable magnesio-mechanical reduction method to prepare high quality silicon nanoparticles with good lithium storage performance using low cost starting materials. Although the reaction of Mg and silica is thermodynamically highly favorable, direct reaction using commercial Mg powder by mechanical milling at room temperature is difficult. However, by adding of 5 wt % Mg2Si, silica nanoparticles can be reduced into Si nanoparticles using commercial Mg as the reductant by mechanical milling at 250 rpm in 5 h. Mechanism study suggests that Mg2Si can effectively break the surface oxide layer of Mg due to its high rigidity modules and create fresh Mg surface to initiate the reaction. The obtained Si nanoparticles and Si@C composites exhibit excellent lithium storage performance comparable to that of the state-of-the-art nano-Si anode materials.