Micro-structured Si@Cu₃Si@C ternary composite anodes for high-performance Li-ion batteries

A micro-structured Si@Cu₃Si@C ternary composite is designed to ease volume expansion of Si as well as to enhance the conductivity of the whole electrode. Structurally, Si particles with carbon shells are agglomerated to form a hierarchical micro-structured ternary component sphere. A benign initial coulombic efficiency (ICE) 70.5% with high reversible capacity after 200 cycles (1477 mAh g⁻¹, 400 mA g⁻¹) of Si@Cu₃Si@C anode can be obtained to demonstrate the superiorities of this structure. This unique porous hierarchical structure can be helpful to facilitate the ions transmission and provide void spaces for stress releasing while improving the conductivity of Si. Carbon shells formed on the Si are available for improving the conductivity of Si electrode and easing some extra side reactions. Cu₃Si alloy acts as a buffer to alleviate the volume expansion of Si. Thus, a comparable stable structure with high conductivity can be maintained for enhancing the performance of Si. In addition, a low vacuum carbonization process is also used for energy saving which might be adopted in other materials fabrication.