Controllable SiOx Coating Layer Promotes High Stable Si Anode for Lithium-Ion Batteries

Silicon (Si) is considered as one of the most promising candidates for next-generation lithium-ion batteries with high energy density. The main problems are the severe volume expansion and continuous interfacial side reaction of Si that hinder its further application. It can be an effective way by constructing a robust coating layer outside of Si to impede/alleviate the above effect. SiO_x with high mechanical strength can largely promote the electrochemical performance of Si. Herein, Si@SiO_x material with high specific surface area, high porosity, and controllable coating was synthesized via a simple solid–liquid reaction by LiOH solution etching effect. The etching/oxidation mechanism of Si under alkaline conditions was thoroughly investigated. The surface oxide layer of Si was beneficial to the formation of a solid electrolyte interphase (SEI) with excellent stability and high Li⁺ conductivity, while its high-porosity structure reduces the volume expansion of the material by approximately 110%. Under the synergistic effect of etching-oxidation, the modified material exhibited superior electrochemical properties. When employed as anode materials, the specific capacity was as high as 3101.5 mAh g^–1 and maintained at 841.0 mAh g^–1 after 500 cycles at 1 A g^–1.