Mg 2 SiO 4 /Si-Coated Disproportionated SiO Composite Anodes with High Initial Coulombic Efficiency for Lithium Ion Batteries.

Silicon monoxide (SiO) is considered as one of the most promising anode material candidates for next-generation high-energy-density lithium ion batteries (LIBs) due to its high specific capacity and relatively lower volume expansion than that of Si. However, a large number of irreversible products are formed during the first charging and discharging process, resulting in a low initial Coulombic efficiency (ICE) of SiO. Herein, we report an economical and convenient method to increase the ICE of SiO without sacrificing its specific capacity by a solid reaction between magnesium silicide (Mg 2 Si) and micron-sized SiO. The reaction product (named MSO) exhibits a unique core-shell structure with uniformly distributed Mg 2 SiO 4 and Si as the shell and disproportionated SiO as the core. MSO exhibits a superior ICE and a high reversible capacity of 81.7% and 1306.1 mAh g -1 , respectively, which can be further increased to 88.7% and 1446.4 mAh g -1 after carbon coating, and improved cyclic stability compared to bare SiO. This work provides a simple yet effective strategy to address the low ICE issue of SiO anode materials to promote the practical application of SiO.