Spontaneous formation of the conformal carbon nanolayer coated Si nanostructures as the stable anode for lithium-ion batteries from silica nanomaterials

Nanostructured-silicon with a conformal carbon coating (Si@C) is a promising anode-material for the next-generation lithium-ion battery (LIB). However, silicon nanostructure and the carbon nanocoating usually are formed in the separated processing steps, making the entire synthesis process costly, complicated and time-consuming. Herein, we propose a process in which silica nanomaterials (i.e., diatomite and stöber sphere) are firstly converted into Mg₂Si. After the converted Mg₂Si further reacts with CaCO₃, a conformal carbon nanolayer (1–5 nm) spontaneously grows on the newly formed Si nanostructures to obtain Si@C. Especially, diatomite-derived Si@C delivers a reversible capacity of 1359.7 mA h g⁻¹ at 4 A g⁻¹, and retains 764.6 mA h g⁻¹ even after 500 cycles. The process reported in this study can provide a scalable way to synthesize high-performance Si@C anode materials for LIBs.