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

A new approach is employed to boost the electrochemical kinetics and stability of vanadium oxygen hydrate (VOH, V2O5·nH2O) 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 in situ 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) vs 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.