Utilizing Cyclic Voltammetry to Understand the Energy Storage Mechanisms for Copper Oxide and its Graphene Oxide Hybrids as Lithium-Ion Battery Anodes

Graphene-based materials have been extensively researched as a means improve the electrochemical performance of transition metal oxides in Li-ion battery applications, however an understanding of the effect of the different synthesis routes, and the factors underlying the oft-stated better performance of the hybrid materials (compared to the pure metal oxides) is not always demonstrated. For the first time, we report a range of synthetic routes to produce graphene oxide (GO)-coated CuO, micro-particle/GO bundles as well as nano-particulates decorated on GO sheets to enable a comparison with CuO and its carbon-coated analogue, as confirmed using scanning electron microscopy (SEM) imaging and Raman spectroscopy. Cyclic voltammetry was utilized to probe the lithiation/delithiation mechanism of CuO by scanning at successively decreasing vertex potentials, uncovering the importance of a full reduction to Cu metal on the reduction step. The GO hybrid materials clearly show enhanced specific capacities and cycling stabilities comparative to the CuO, with the most promising material achieving a capacity of 746 mAh g(-1) and capacity retention of 92 % after 30 cycles, which is the highest stable capacity quoted in literature for CuO. The simple cyclic voltammetry technique used in this work could be implemented to help further understand any conversion-type anode materials, in turn accelerating the research and industrial development of conversion anodes.