Sub-10-nm Co₃O₄ nanoparticles/graphene composites as high-performance anodes for lithium storage

To improve the electrochemical performance of Co₃O₄/graphene composites towards high-performance lithium ion batteries, various facile chemical methods have been developed to form hybrid Co₃O₄/graphene composites, but the compositions of these composites were considerably different. In this study, a two-step solvothermal synthesis method was employed to accurately control the concentration of Co₃O₄ nanoparticles (NPs) with particle sizes less than 10 nm in the composite. The Co₃O₄/reduced graphene oxide (RGO) composites exhibited the highest reversible capacity of 1600 mAh g⁻¹ at 43 wt% Co₃O₄ NPs. The synergic effects of the sub-10-nm sized Co₃O₄ and the RGO sheets resulted in improved reversible capacity, cycling stability, and rate capability, which are caused by a large number of active sites and the short diffusion pathways provided by the nano-sized Co₃O₄, as well as the elastic buffer space and conductive pathway provided by the RGO sheets.