Engineering Interlayer Space and Composite of Square-Shaped VO by PVP-Assisted Polyaniline Intercalation and Graphene for Aqueous Zinc-Ion Batteries.

VO undergoes irreversible phase transition and collapse of layered structure during the Zn insertion/extraction, which severely limits its application as a cathode for aqueous zinc-ion batteries (AZIBs). Herein, a synergistic strategy of conductive polyaniline insertion and graphene composite was proposed to boost the Zn storage performance of the VO cathode. A square-shaped polyaniline (PANI)-intercalated and graphene-composited vanadium oxide (GO/PANI-PVP/VO) structure was successfully synthesized via an in situ oxidation/insertion polymerization combined with a hydrothermal method. The results showed that PANI intercalation and the composite of graphene combined with layered VO, enabling reversible intercalation of Zn/H. The insertion of conjugated PANI not only increases the lattice spacing of VO, providing a channel for rapid transport of Zn, but also increases the storage sites for charges through doping/dedoping processes and redox conversion reactions. GO/PANI-PVP/VO delivers an excellent specific capacity (495 mA h g at 0.1 A g), wonderful rate capability (208 mA h g at 30 A g), and good cycling stability (93% after 4000 cycles). Our results provide a new approach for adjusting the valence states, interlayer spacing, and rational design of organic-inorganic compound materials for different functional materials.