Efficient conversion of montmorillonite-derived porous nano-silica to nano-silicon for lithium-ion battery anodes

Abstract

Abstract Nano-silicon has been regarded as the most promising anode material for next-generation lithium-ion batteries (LIBs). However, the preparation of nano-silicon suffers from high cost, complex procedures, and low yield, which hinders its commercial application. In this study, porous nano-silicon with particle sizes in the range of 50–100 nm was prepared through molten salt-assisted magnesiothermic reduction using porous nano-silica derived from clay minerals as the precursor. Through combining ball milling and acid activation, the synthesised nano-silica derived from montmorillonite exhibited smaller particle sizes (below 50 nm), higher specific surface area (647 m 2 g –1 ), and total pore volume (0.71 cm 3 g –1 ). This unique structure greatly facilitated the conversion efficiency of silica into nano-silicon by maximising the contact area between silica and magnesium powder and optimising the diffusion kinetics of magnesium atoms. When used as anodes in LIBs, the synthesised nano-silicon materials demonstrated a high specific capacity of up to 1222 mAh g –1 and an excellent capacity retention rate of 79% after 150 cycles at a current density of 0.5 A g –1 . This method provides a novel approach for the cost-effective and large-scale production of nano-silicon materials for high-performance anodes.