Synthesis,Structure Transformation,and Electrochemical Properties of Li2MgSi as a Novel Anode for Li‐lon Batteries

In this work, a novel hexagonal Li₂MgSi anode is successfully prepared through a hydrogen‐driven chemical reaction technique. Electrochemical tests indicate significantly improved cycling stability for the as‐synthesized Li₂MgSi compared with that of Mg₂Si. Ball‐milling treatment induces a polymorphic transformation of Li₂MgSi from a hexagonal structure to a cubic structure, suggesting that the cubic Li₂MgSi is a metastable phase. The post‐24‐h‐milled Li₂MgSi delivers a maximum capacity of 807.8 mAh g^?1, which is much higher than that of pristine Li₂MgSi. In particular, the post‐24‐h‐milled Li₂MgSi retains 50% of its capacity after 100 cycles, which is superior to cycling stability of Mg₂Si. XRD analyses correlated with CV measurements do not demonstrate the dissociation of metallic Mg and/or Li–Mg alloy involved in the lithiation of Mg₂Si for the Li₂MgSi anode, which contributes to the improved lithium storage performance of the Li₂MgSi anode. The findings presented in this work are very useful for the design and synthesis of novel intermetallic compounds for lithium storage as anode materials of Li‐ion batteries.