LAUSR

Abstract A facile strategy to control the interfacial energy at graphite-water interface is introduced by coating the hydrophobic graphite powder with a hydrophilic manganese oxide layer. This modification not only improves the aqueous dispersion stability of graphite particles, but also supplements the low lithium ion storage capacity of graphite due to the high lithium ion uptake capability of manganese oxide. A catalytic reaction between graphite particles and permanganate ions leads to the formation of MnO2 layer on the surface of graphite particles. Successively, annealing the resulting composite powder in a reducing atmosphere transforms surface MnO2 to MnO. The electrode prepared with MnO-coated graphite powder showed the specific capacitance of 402 mAh g−1 at a current density of 25 mA g−1, which is higher than that of the pristine graphite electrode (338 mAh g−1 at 25 mA g−1). In addition, the electrode exhibited outstanding charge–discharge cycling stability for 100 cycles at a current density of 100 mA g−1 without any fluctuation or abnormal increase in the capacity that is often observed in transition metal oxide-based electrodes. It also showed excellent rate capability comparable to the pristine graphite electrode.