CoO/ZnO nanoclusters immobilized on N-doped 3 D reduced graphene oxide for enhancing lithium storage capacity

Cobalt oxide (CoO) with high theoretical capacity is a potential anode material for lithium ion batteries (LIBs), however its application is limited by high cost and volume expansion. Considering the cheapness of Zn and advantages of bimetallic oxide compounds, CoO/ZnO nanoclusters immobilized on N-doped 3 D reduced graphene oxide (CoO/ZnO-NrGO) were constructed by facile solvothermal and freeze-drying method as the LIBs anode for improving lithium (Li) ions storage. Three-dimensional conductive network structure not only reduced the volume expansion of CoO and ZnO but also accelerated the transfer rate of Li ions. Besides, nitrogen doping provided more active sites for plentiful Li ions storage. Phase composition and microstructure of CoO/ZnO-NrGO were measured by X-ray photoelectron spectroscopy, transmission electron microscopy, Raman spectroscopy, X-ray diffraction and so on. Synchronously, electrochemical property of CoO/ZnO-NrGO was also tested. It was found that the specific capacity of CoO1.2/ZnO0.6-NrGO6.78 was 1494 mA h g−1 at 0.1 A g−1, higher that of other bimetallic oxides such as CoO–MnO, CoO–Co3O4, CoO–CoFe2O4 and so on. The capacity of CoO1.2/ZnO0.6-NrGO6.78 was maintained approximately 600 mA h g−1 at 2.0 A g−1 after 1000 cycles. Taking these advantages into account, composites of bimetallic oxides and carbon material with high specific capacity provide a novel idea for a new generation of LIBs.