Ultrafine nano-Si material prepared from NaCl-assisted magnesiothermic reduction of scalable silicate: graphene-enhanced Li-storage properties as advanced anode for lithium-ion batteries

Abstract

Herein, ultrafine nano-Si has been prepared via a NaCl-assisted magnesiothermic reduction with scalable silicate as Si source. In the high-temperature procedures of magnesiothermic reduction, as an effective heat scavenger, adjuvant NaCl promote the formation of interconnected Si nanoparticles with ultra-small size of 5–10 nm. When used as anode materials for lithium-ion batteries, reduced graphene oxide (rGO) plays a significant role in enhancing the electrochemical performance due to its high conductivity and flexibility by forming the nano-Si/rGO composite. The nano-Si/rGO composite exhibits much improved Li-storage properties in terms of superior high-rate capabilities and excellent cycle stability compared to the pure nano-Si as well as the micro-Si prepared from no addition of NaCl. It can deliver a high specific capacity of 1955 mA h g−1 at 100 mA g−1 with high initial columbic efficiency of >80%. In addition, nano-Si/rGO exhibits superior rate capability (891 mA h g−1 at 5 A g−1). The significantly enhanced Li-storage properties could be attributed to the synergistic effects of highly conductive rGO and nanosized Si particles in the nano-Si/rGO. While the former can improve the electrical conductivity, the latter will decrease the Li+ diffusion length, improve the capacity and optimize the cycling stability.