Reaction mechanism and enhancement of cyclability of SiO anodes by surface etching with NaOH for Li-ion batteries

Abstract

SiO has been considered as one of the most promising anodes, the reaction mechanism of SiO with Li is still not well understood. High energy mechanical milling (HEMM) followed by etching of the SiO surface with NaOH solution was carried out in this study to enhance cycle performance. X-ray photoelectron spectroscopy (XPS) analyses showed the different compositions of the Si valence state before and after sputtering, and the atomic ratio of O/Si at the surface differed from that of the inside bulk SiO. Using high resolution transmission electron microscopy (HRTEM), the reaction mechanism of a SiO electrode was investigated. During the first discharge, Li₂Si₂O₅ and Li₆Si₂O₇ phases were identified as well as Li₄SiO₄ and Li rich amorphous binary Li_xSi phases. The surface etched SiO showed significantly better cyclability with the reversible capacity of 1260 mA h g⁻¹ over 50 cycles.