Defect-domains enabling VO2 nanosheet arrays with fast charge transfer for 3.0 V aqueous supercapacitors

Defective metal oxides are of great significance to promote reaction activity for high energy and power densities supercapacitors in aqueous electrolytes. Herein, we demonstrate a monoclinic VO2 nanosheet arrays electrode with tailorable defect-domains by a simple thermal-induced strategy. It is found that the defect-domains stemmed from the residual trivalent vanadium of V2O3 precursor directly influence the intrinsic conductivity of VO2. The relationships between defect-domains and electrochemical performance are built and the defect-optimized VO2 can greatly accelerate the electrochemical reaction kinetics with decreased polarization effect. It exhibits a high specific capacitance of 180.3 F g(-1) at 0.5 A g(-1) and 78.8 F g(-1) even at 10 A g(-1) within a large potential window of -1.5 similar to 0.15 V with superior cycle stability in water in salt electrolyte. A 3.0 V aqueous asymmetric supercapacitor device is assembled with MnO2 nanosheet arrays as cathode, which delivers a very high energy density of 120.3 Wh kg(-1) at 1.5 kW kg(-1) , almost as good as sodium/potassium ion batteries.

Automated summary

Defective metal oxides play a crucial role in enhancing the reaction activity of supercapacitors in aqueous electrolytes. By optimizing the defects in VO₂ nanosheets, the electrochemical performance can be greatly improved, leading to high specific capacitance and stability. An aqueous asymmetric supercapacitor device assembled with MnO2 nanosheets demonstrates a high energy density comparable to sodium/potassium ion batteries.