Chemically integrated hierarchical hybrid zinc cobaltate/reduced graphene oxide microspheres as an enhanced lithium-ion battery anode

Abstract

Chemically integrated hierarchical microsphere ZnCo₂O₄/reduced graphene oxide hybrid composites are synthesized via a polyol process. Microsphere ZnCo₂O₄ particles embedded in graphene homogeneously with sizes in the region of 320–512 nm, graphene sheets grew and interwove inversely in the inside of the microsphere ZnCo₂O₄ particles, so that the structure possesses a unique microsphere–sheet hybrid structure. The interconnected graphene conductive network basic skeleton is beneficial to the transportation of Li⁺ and electrons. Compared with the conventional way metal oxides and graphene combine, hierarchical microsphere ZnCo₂O₄/reduced graphene oxide hybrid composites exhibit enhanced rate capability (469.7 mA h g⁻¹ at 4000 mA g⁻¹) and long term cycling ability with high capability (904.2 mA h g⁻¹ at 1000 mA g⁻¹ over 500 charge/discharge cycles), owing to the special characteristic of a three-dimensional structure. Most importantly, with the successful synthesis of the hierarchical microsphere ZnCo₂O₄/reduced graphene oxide hybrid composites, this facile strategy can extend to the synthesis of the ternary transition metal oxides/reduced graphene oxide with hierarchical microsphere structure and make it possible to explore a more promising storage application.