Milled-Si@C Composites as Potential Anode Materials for Li-ion Batteries

Abstract

Silicon (Si) has been identified as having high potential for lithium-ion battery anodes because of its ultrahigh capacity. However, its dramatic volume change in the process of lithiation/delithiation and its intrinsically poor electrical conductivity have severely inhibited its practical application. Herein, micron-sized Si alloys with carbon shells are prepared by high-energy ball milling coupled with an evaporation self-assembly method. A high and stable specific capacity of 850.5 mAh/g is achieved over 50 cycles and held at 650 mAh/g after 350 cycles with a coulombic efficiency >99.8%. The highly improved performance could be attributed to the unique microstructure of the as-synthesized composite materials in which crystalline Si nanoparticles are embedded in amorphous Si-M2O3 (M = Al and Si) matrix phases with a carbon shell on the surface, thereby achieving better buffering capacity and conductivity. The results we obtained could pave the way for using silicon as anodes for lithium-ion batteries.