Controllable SiO<sub><i>x</i></sub> Coating\nLayer Promotes High Stable Si Anode for Lithium-Ion Batteries

Silicon (Si) is considered as one of the most promising\ncandidates\nfor next-generation lithium-ion batteries with high energy density.\nThe main problems are the severe volume expansion and continuous interfacial\nside reaction of Si that hinder its further application. It can be\nan effective way by constructing a robust coating layer outside of\nSi to impede/alleviate the above effect. SiO<sub><i>x</i></sub> with high mechanical strength can largely promote the electrochemical\nperformance of Si. Herein, Si@SiO<sub><i>x</i></sub> material\nwith high specific surface area, high porosity, and controllable coating\nwas synthesized via a simple solid–liquid reaction by LiOH\nsolution etching effect. The etching/oxidation mechanism of Si under\nalkaline conditions was thoroughly investigated. The surface oxide\nlayer of Si was beneficial to the formation of a solid electrolyte\ninterphase (SEI) with excellent stability and high Li<sup>+</sup> conductivity,\nwhile its high-porosity structure reduces the volume expansion of\nthe material by approximately 110%. Under the synergistic effect of\netching-oxidation, the modified material exhibited superior electrochemical\nproperties. When employed as anode materials, the specific capacity\nwas as high as 3101.5 mAh g<sup>–1</sup> and maintained at\n841.0 mAh g<sup>–1</sup> after 500 cycles at 1 A g<sup>–1</sup>.