Cooperative Energy Storage Behaviors Derived from Pani Nanosheets and V2ctx Mxene for Advanced Aqueous Zinc-Ion Batteries

The diversity of vanadium-based cathode materials have been exploited to relieve the capacity decay of rechargeable aqueous zinc-ion batteries along with the extension of current densities and life cycles. Herein, polyaniline nanosheets were anchored to the surface of O-V2CTx MXene to arrange a three-dimensional architecture of hybrid composites via an electrostatic self-assembly process. The accessible surface of O-V2CTx MXene derived from the emergence of vanadium-oxygen terminations in the opening aqueous suspension contributes to attracting positively charged polyaniline nanosheets, followed by the transformation of V-C to V3+ and V4+ species on the surface of O-V2CTx MXene through an in situ oxidation process. The intercalation of polyaniline nanosheets as spacing blocks into the interlayer region between O-V2CTx nanosheets is capable to suppress the re-stacking of O-V2CTx MXene in favor of accelerating Zn2+ ion diffusion processes and enrich surface electrochemical active sites of O-V2CTx MXene in dependence on cooperative charge storage processes between heterogeneous constituents. The result shows that PANI/O-V2CTx composites achieve a reversible capacity of 267.7 mAh g-1 at 0.2 A g-1 in comparison with those of 135.1 mAh g-1 for PANI and 116.2 mAh g-1 for O-V2CTx MXene. After 2000 cycles, PANI/O-V2CTx composites also exhibit the excellent cycling stability with a high capacity retention of 91.8% at 5 A g-1. Moreover, the results from ex situ XRD patterns and XPS spectra reveal the realization of the reversible redox transformation between V4+ and V5+ species on the surface vanadium-oxygen coating of O-V2CTx MXene with the aid of electrochemical active PANI.