Magnesiated Si-Rich SiOx Materials for High-Performance Lithium-Ion Batteries

Abstract

Silicon monoxide (SiO)-based materials have significant potential as high-capacity anode materials for lithium-ion batteries (LIBs). However, the low initial Coulombic efficiency (ICE) associated with the irreversible electrochemical reaction of the amorphous SiO2 phase (a-SiO2) in SiO hinders its application in commercial LIBs. The preemptive phase transition of a-SiO2 to an inactive silicate phase using a metal hydride is a promising strategy for improving the ICE. However, this process inevitably leads to reversible capacity loss. In this study, a high-capacity Si-rich SiOx composite prepared by high-energy mechanical milling is premagnesiated using MgH2, resulting in a significantly improved capacity and ICE compared to those of pristine SiO and Si-rich SiOx composites. The resulting Si/Mg2SiO4 composite electrode exhibited a high initial discharge capacity of 1961 mAh g-1 with a high ICE of 87.0% and maintained highly stable capacity retention after 200 cycles compared to the Si-rich SiOx. These improved electrochemical properties are attributed to the preemptively synthesized Mg2SiO4, which not only prevents irreversible reactions between lithium and a-SiO2 during the initial lithiation but also acts as a buffer phase that effectively reduces volume expansion during cycling.