High-Performance Aqueous Zinc-Ion Batteries Enabled by Binder-Free and Ultrathin VO@Graphene Aerogels with Intercalation Pseudocapacitance.

As a result of the absence of solid-state diffusion limitation, intercalation pseudocapacitance behavior is emerging as an attractive charge-storage mechanism that can greatly facilitate the ion kinetics to boost the rate capability and cycle stability of batteries; however, related research in the field of zinc-ion batteries (ZIBs) is still in the initial stage and only found in limited cathode materials. In this study, a novel VO@rGO hybrid aerogel consisting of ultrathin VO nanosheets (∼1.26 nm) with abundant oxygen vacancies (Vö) and a three-dimensional (3D) graphene conductive network was specifically designed and used as a freestanding and binder-free electrode for ZIBs. As expected, the ideal microstructure of both the material and the electrode enable fast electron/ion diffusion kinetics of the electrode, which realize a typical intercalation pseudocapacitance behavior as demonstrated by the simulation calculation of cyclic voltammetry (CV), ex situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and first-principles density functional theory (DFT) calculation. Thanks to the elimination of solid-state diffusion limitation, the VO@rGO electrode delivers a high reversible rate capacity of 153.9 mAh g at 15 A g and 90.6% initial capacity retention at 0.5 A g after 1050 cycles in ZIBs. The intercalation pseudocapacitance behavior is also realized in the assembled soft-pack battery, showing promising practical application prospects.