Cooperative energy storage behaviors derived from PANI and V2CTx MXene for advanced aqueous zinc-ion batteries

Polyaniline (PANI) 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 PANI, followed by the transformation of C-V/V2+ to V3+ and V4+ species on the surface of O-V2CTx MXene through an in situ oxidation process. The intercalation of PANI 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+ 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, ex situ structural characterizations 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.