Boosting operating voltage of vanadium oxide-based symmetric aqueous supercapacitor to 2 V.

Graphical abstract Highlights • FC NWA substrate fabrication as a 3D conductive carbon scaffold. • Electrochemical growth of vanadium oxide nanowires on FC NWA substrate. • Enlarged charge storage window for the composite through vanadium valence tuning. • The assembled symmetric supercapacitor works with a high voltage of 2 V. Abstract Vanadium oxides have great potentials in high voltage symmetric supercapacitors, benefiting from the available multiple oxidation states of vanadium. In this work, charge storage in a wide potential window of −1.1 to 0.9 V vs. SCE is achieve for vanadium oxide through vanadium valence tuning and incorporation in functionalized carbon nanowire array. The functionalized carbon nanowire array provides a good three dimensional conductive scaffold for the oxide nanowires, leading to high electron and ion transportation for the pseudo-capacitive materials. A high areal capacitance of 1.31 F cm−2 is achieved for the obtained vanadium oxide electrode (at 1 mA cm−2 in 5 M LiCl aqueous solution). It also displays good rate capability, demonstrating a quite high areal capacitance of 687 mF cm−2 at 100 mA cm−2. The assembled symmetric supercapacitor can be operate with a large voltage of 2 V and so can deliver a high volumetric energy density of 3.61 mWh cm−3 at 0.01 W cm−3. The supercapacitor also shows good stability, it can retain 91% of its capacitance after 10 000 galvanostatic charge-discharge cycles. [ABSTRACT FROM AUTHOR]