High energy density asymmetric quasi-solid-state supercapacitor based on porous vanadium nitride nanowire anode.

To push the energy density limit of asymmetric supercapacitors (ASCs), a new class of anode materials is needed. Vanadium nitride (VN) holds great promise as anode material for ASCs due to its large specific capacitance, high electrical conductivity, and wide operation windows in negative potential. However, its poor electrochemical stability severely limits its application in SCs. In this work, we demonstrated high energy density, stable, quasi-solid-state ASC device based on porous VN nanowire anode and VOx nanowire cathode for the first time. The VOx//VN-ASC device exhibited a stable electrochemical window of 1.8 V and excellent cycling stability with only 12.5% decrease of capacitance after 10,000 cycles. More importantly, the VOx//VN-ASC device achieved a high energy density of 0.61 mWh cm(-3) at current density of 0.5 mA cm(-2) and a high power density of 0.85 W cm(-3) at current density of 5 mA cm(-2). These values are substantially enhanced compared to most of the reported quasi/all-solid-state SC devices. This work constitutes the first demonstration of using VN nanowires as high energy anode, which could potentially improve the performance of energy storage devices.