2D Layered VSe2 with High Pseudocapacitive Zn-ion Storage as Cathode for High-Power Zinc-ion Batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) are attractive storage solution for renewable energy storage systems (ESS) applications. Despite intrinsic safety, eco-friendliness, and low cost of aqueous ZIBs, their practical application is severely hindered by unavailability of high capacity and robust cathode materials. Vanadium-based cathodes with various structures, large layer spacing, and different oxidation states are considered suitable cathode candidates for ZIBs. In this work we studied 2D layered VSe2 with high pseudocapacitive mediated Zn-ion storage as cathode for aqueous Zinc-Ion Batteries. The VSe2 cathode reversibly hosted Zinc ion with a capacity of 205 mAh g-1 at 0.2 A g-1, maintaining a capacity of 135 mAh g-1 at 8 A g-1, and stability of 98% after 600 cycles at 1 A g-1, favoured by 2D layered structure with defects and metallic conducting nature. Zn-ion storage mechanism and kinetics in the cathode is examined using ex-situ XRD, XPS, TEM, and GITT studies, and it is found that the favourable interlayer spacing with structural defects efficiently stored Zn-ion through high contribution from capacitive mediated storage. The favourable architecture enables fast Zn-ion diffusion, high capacity at high current rate along with good stability. The current work emphasizes on the potential of rational design of several transition metal dichalcogenides based cathode with strong pseudocapacitive storage for sustainable energy storage system like aqueous ZIB.