Engineering V2O3 nanoarrays with abundant localized defects towards high-voltage aqueous supercapacitors

Abstract

Exploiting high-capacitance and more negative potential anode materials is pivotal to the breakthrough of energy density for aqueous supercapacitors. In this work, we demonstrated the localized defect engineering of Mo-doped V₂O₃ nanoarrays with abundant V⁴⁺ around Mo-ions. The localized defect engineering remarkably reduces the energy barrier of V-ion redox reactions and broadens the work potential window, thereby greatly increasing the energy density. The target sample delivers a specific capacitance of 333.9 F g⁻¹ at 1.0 A g⁻¹ within −1.2–0.2 V (vs. Ag/AgCl) in a LiTFSI aqueous electrolyte, about 3 times higher than that of the corresponding V₂O₃ nanoarrays. Electrochemical quartz crystal microbalance (EQCM) directly exhibits a triple increase in the adsorption capacity of cations under a 100% charging state. When assembled into aqueous supercapacitors with a MnO₂ nanosheet cathode, it can be operated at a very large potential window up to 2.7 V with an energy density as high as 149.9 W h kg⁻¹ at 1.35 kW kg⁻¹, which is among the best report for aqueous supercapacitors.