Water-Processable and Multiscale-Designed Vanadium Oxide Cathodes with Predominant Zn²⁺ Intercalation...

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 Zn²⁺ /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 V₂ O₅ nanoflakes is developed, and therein, large pseudocapacitance via predominant (≈91%) Zn²⁺ intercalation is revealed. Besides competitive gravimetric/areal capacity, the binder-free cathodes exhibit high volumetric capacity of 1106.1 mAh cm^-3 and high-rate capability of 180.0 mA g^-1 at 30 A g^-1 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 Zn²⁺ storage, but the least hydroxyl terminated surface for H⁺ insertion, as well as highly conductive network for electron transfer and fast Zn²⁺ 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.