Aqueous Al-Ion Supercapacitor with V2O5 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 efficient energy storage. MCM/V₂O₅ composites exhibit high dispersion of nanostructured V₂O₅ in a 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.