Graphite fluoride as a cathode material for primary magnesium batteries with high energy density

Graphite fluorides have become promising electrode materials for lithium batteries while their applications in magnesium batteries are rarely reported. Here we demonstrate for the first time CF0.8 as a cathode material for magnesium batteries with a high discharge capacity of more than 800 mAh g−1. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and the charge/discharge measurements are used to characterize its structure and electrochemical performance. SEM indicates that CF0.8 sample is a layered structure with the thickness of approximately 300∼400 nm. The CF0.8 cathode exhibits a high discharge capacity of 813.4 mAh g−1 after discharging to 0.5 V at 20 mA g−1 in 0.4 M (PhMgCl)2-AlCl3/THF electrolyte (named as APC/THF). Discharge product MgF2 is confirmed by EDX and XPS measurements. Addition of LiCl to APC/THF solution can not only enhance the gravimetric energy densities but also greatly improve the rate performance. The possible function mechanism is proposed and discussed.