Tuning ionic conduction and structure stability of ammonium vanadate by intercalating polyaniline molecules for advanced aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) are regarded as a potential green storage system due to their environmental friendliness, intrinsic safety and low cost. However, cathode materials are still facing enormous challenges in practical application because of unsatisfactory energy storage properties. Compared with vanadium oxides, ammonium vanadate (NH4V4O10) is considered to be more potential due to its relatively larger interlayer spacing and more stable structure. For further boosting its rate capability and cycling stability, NH4V4O10 with polyaniline (PANI) intercalation is fabricated by a hydrothermal method and subsequent in situ polymerization in this work. Benefiting from the large lattice distance of NH4V4O10, the aniline monomer can enter the interlayer rapidly and perform in situ polymerization by reacting with V5+. The results show that the intercalated PANI not only enlarges the interlamellar spacing (13.59 angstrom) by improving the diffusion efficiency of Zn2+ and enhances electronic conductivity but also stabilizes the crystal structure. Therefore, the NVO/PANI120 electrode displays an outstanding rate performance of 308.06 mA h g(-1) at 10 A g(-1) (71.01% as the current density increases 100 times) and long-term cycle life (92.23% over 5000 cycles at 5 A g(-1)). Moreover, numerous ex situ characterization studies are carried out to investigate the reversible Zn2+ insertion/extraction process of NVO/PANI120. In brief, our work proves the feasibility of PANI intercalation into ammonium vanadate and provides a novel choice for designing high-performance cathode materials for other multivalent ion batteries.