Protective carbon-coated silicon nanoparticles with graphene buffer layers for high performance anodes in lithium-ion batteries

Silicon is a promising anode material for use in lithium-ion batteries (LIBs). However, its volume expansion problem can cause critical issues that deteriorate efficiency, cycle life, and result in sudden breakage of battery cells. Herein, polyethylene glycol derived thin carbon-coated Si nanoparticles (Si/c-PEG) and graphene wrapping were used to block electrolyte contact and buffer volume changes, respectively. The hierarchical graphenewrapped Si/c-PEG (Si/c-PEG/G) exhibited outstanding performance with a gravimetric capacity of similar to 1820 mAh/g at 0.1 A/g and 99.5% Coulombic efficiency at the 10th cycle. Moreover, the full-cell configuration using Si/cPEG/G anodes with commercial lithium cobalt oxides (LiCoO2, LCO) cathodes demonstrated stable operation during repeated charge/discharge cycles at 0.1 and 1 C rates. Micelle coating of PEG with graphene layers was a useful method for minimizing the exposed area of silicon to the electrolyte during lithium-ion storage.