Aqueous Al-Ion Supercapacitor with V 2 O 5 Mesoporous Carbon Electrodes.

A high-performance low-cost aqueous Al-ion supercapacitor was fabricated based on nanostructured V2O5 impregnated mesoporous carbon microspheres (MCM/V2O5) electrodes and Al2(SO4)3 electrolyte for the efficient energy storage. MCM/V2O5 composites exhibit high dispersion of nanostructured V2O5 in mesoporous carbon matrix, beneficial to fast reversible redox reactions with a short diffusion path. The corresponding capacitor illustrates the distinguishable redox behavior, most likely due to the Al3+ intercalation/deintercalation leading to the reduction/oxidation of V5+/V4+. It delivers a high energy density of 18.0 Wh kg-1 at 147 W kg-1 and a long cycling lifespan with over 88% capacitance retention over 10,000 cycles. The competitive performance can be ascribed to the integration of the electric double layer capacitance provided from MCM with pseudocapacitance contributed by nanostructured V2O5. This work offers the possibilities of high-performance aqueous capacitors based on trivalent Al-ion as guest species, providing new directions for future development of supercapacitors.