Resilient Yolk-Shell Silicon-Reduced Graphene Oxide/Amorphous Carbon Anode Material from a Synergistic Dual-Coating Process for Lithium-Ion Batteries

A dual-coating process was developed to prepare a unique yolk-shell silicon-reduced graphene oxide/amorphous carbon (YS-Si@rGO/a-C) anode material. The nanostructured Si composite anode material consists of Si cores, evenly wrapped with a first coating of graphene oxide constructed through electrostatic self-assembly, and a shell of a second reinforced coating of graphene oxide/amorphous carbon, integrated by using an economic hydrothermal carbonization process. Thermal reduction and HF etching were then applied to reduce graphene oxide into graphene and to create the required void space to endow the hybrid material with sufficient mechanical strength and to buffer against stresses induced by volume changes of the Si nanoparticles. The obtained YS-Si@rGO/a-C composite anode material has structural integrity together with conductive 3D-network beneficial to its electrochemical performance, attributed to the synergy of electrostatic self-assembly and hydrothermal carbonization. As a result, the composite anode has a superior initial coulombic efficiency of 76%, surpassing other published Si/G composite anodes, as well as an initial cycle reversible capacity of 1668mAhg(-1) at 0.4Ag(-1) and a capacity retention of 75% after over 100 cycles, when compared with the yolk-shell structured Si@a-C anode.