Crystallization of Zinc Oxide Quantum Dots on Graphene Sheets as Anode Material for Lithium ion Batteries

A zinc oxide quantum dot/reduced graphene oxide composite (ZnO/RGO) is prepared for the first time by a stepped graphene oxide (GO) reduction strategy. Only metal zinc and few-layer GO aqueous suspension are used as starting materials. GO sheets are partially reduced by metal zinc and Zn(OH)2 quantum dots are in return generated in the first room temperature Zn reduction step. Zn(OH)2 quantum dots are subsequently transformed to ZnO quantum dots, which catalyzes the deoxygenation of the remaining oxygen-containing groups on GO sheets to obtain the final ZnO/RGO product in the second step at 95 °C. As a result, homogeneously distributed ZnO quantum dots with an average particle size below 10 nm are firmly anchored on the surface of RGO sheets to constitute a micro-sized thin ZnO/RGO composite. The ZnO/RGO composite delivers both high reversible capacities and long cycle life as anode material for lithium ion batteries.