Vo2/Graphene Oxide Composite as a Cathode Material with High Rate Performance for Hybrid Mg-Li Batteries

Rechargeable magnesium batteries (RMBs) can meet the urgent demand for large-scale energy storage systems due to their high volumetric energy density, safety, and low cost. RMB development requires the exploitation of cathode materials with high specific capacities and potentials. Layered VO2 is a promising cathode material for RMBs due to its high capacity (>200 mAh g−1) and high voltage (>1.5 V). However, the diffusion kinetics of Mg2+ in the VO2 host are sluggish, which results in poor electrochemical performance. In this study, a VO2/graphene oxide (VO2/GO) composite was constructed via a facile ultrasonication method combined with freeze drying as a cathode material for rechargeable hybrid Mg2+/Li+ batteries (HMLBs). The VO2/GO cathode material has a high discharge capacity (261.7 mAh g−1 at 20 mA g−1), significant discharge platform (above 1.75 V), and satisfactory cycling capacity. The capacity retention of the cathode was maintained at 83% after 200 cycles at 100 mA g−1. Ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were used to study the Mg2+ storage mechanism of the VO2/GO electrode during the charging and discharging processes.