2D layered VSe2 with high pseudocapacitive Zn-ion storage as a cathode for high-power zinc-ion batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) are an attractive storage solution for renewable energy storage system (ESS) applications. Despite the intrinsic safety, eco-friendliness, and low cost of aqueous ZIBs, their practical application is severely hindered by the unavailability of high-capacity and robust cathode materials. Vanadium-based cathodes with various structures, large layer spacing, and different oxidation states are considered to be suitable cathode candidates for ZIBs. In this work, we studied 2D layered VSe₂ with high pseudocapacitive-mediated Zn-ion storage as a cathode for aqueous zinc-ion batteries. The VSe₂ cathode reversibly hosted zinc ions 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 a stability of 98% after 600 cycles at 1 A g⁻¹, favoured by its 2D layered structure with defects and metallic conducting nature. The Zn-ion storage mechanism and kinetics in the cathode are 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-ions through a high contribution from capacitive-mediated storage. The favourable architecture enables fast Zn-ion diffusion and high capacity at a high current rate with good stability. The current work emphasizes the potential for the rational design of several transition-metal–dichalcogenide-based cathodes with strong pseudocapacitive storage for sustainable energy storage systems such as aqueous ZIBs.