Water-Processable and Multiscale-Designed Vanadium Oxide Cathodes with Predominant Zn Intercalation Pseudocapacitance toward High Gravimetric/Areal/Volumetric Capacity.

Layered vanadium oxides have great potential as cathode materials for recently surged aqueous zinc-ion batteries (AZIBs). However, achieving high energy/power densities simultaneously is challenging, and side reactions related to more frequently than disclosed Zn /proton co-insertion mechanism aggravate stability concerns. Herein, an engineered binder-free cathode configuration based on water-processable and high packing-density sheet-shaped composites of carbon nanotubes network, surface poly(3,4-ethylenedioxythiophene) (PEDOT) bridging coating, and ultrasmall PEDOT-intercalated V O nanoflakes is developed, and therein, large pseudocapacitance via predominant (≈91%) Zn intercalation is revealed. Besides competitive gravimetric/areal capacity, the binder-free cathodes exhibit high volumetric capacity of 1106.1 mAh cm and high-rate capability of 180.0 mA g at 30 A g as well as long-cycling stability. Such combined level of performance and unwanted reaction mechanism are attributed to the contained multiscale material/electrode design formula from crystal structure modification to 3D architecture construction of whole electrode, which endows the binder-free cathodes with abundant accessible sites for Zn storage, but the least hydroxyl terminated surface for H insertion, as well as highly conductive network for electron transfer and fast Zn diffusion kinetics throughout the electrode. Combined with scalable fabrication protocols, this study opens up great opportunities for high-performance vanadium oxide cathodes practically applicable to AZIBs.