Graphene-like Vanadium Oxygen Hydrate (VOH) Nanosheets Intercalated and Exfoliated by Polyaniline (PANI) for Aqueous Zinc-Ion Batteries (ZIBs)

Abstract

A new approach is employed to boost the electrochemical kinetics and stability of vanadium oxygen hydrate (VOH, V₂O₅·<i>n</i>H₂O) employed for aqueous zinc-ion battery (ZIB) cathodes. The methodology is based on electrically conductive polyaniline (PANI) intercalated-exfoliated VOH, achieved by preintercalation of an aniline monomer and its <i>in situ</i> polymerization within the oxide interlayers. The resulting graphene-like PANI-VOH nanosheets possess a greatly boosted reaction-controlled contribution to the total charge storage capacity, resulting in more material undergoing the reversible V⁵⁺ to V³⁺ redox reaction. The PANI-VOH electrode obtains an impressive capacity of 323 mAh g^-1 at 1 A g^-1, and state-of-the-art cycling stability at 80% capacity retention after 800 cycles. Because of the facile redox kinetics, the PANI-VOH ZIB obtains uniquely promising specific energy-specific power combinations: an energy of 216 Wh kg^-1 is achieved at 252 W kg^-1, while 150 Wh kg^-1 is achieved at 3900 W kg^-1. Electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) analyses indicate that with PANI-VOH nanosheets, there is a simultaneous decrease in the charge transfer resistance and a boost in the diffusion coefficient of Zn²⁺ (by a factor of 10-100) <i>vs</i> the VOH baseline. The strategy of employing PANI for combined intercalation-exfoliation may provide a broadly applicable approach for improving the performance in a range of oxide-based energy storage materials.