Crystallization of zinc oxide quantum dots on graphene sheets as an anode material for lithium ion batteries

Abstract

A zinc oxide quantum dot/reduced graphene oxide (ZnO/RGO) composite 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 into ZnO quantum dots, which catalyze 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 of 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 an anode material for lithium ion batteries.