Organic Dye Molecule Intercalated Vanadium Oxygen Hydrate Enables High-Performance Aqueous Zinc-Ion Storage

Although the layered vanadium oxide-based materials have been considered to be one of the candidates for aqueous Zn-ion batteries (AZIBs), it still faces inevitable challenges of unsatisfactory capacities and sluggish kinetics because of strong electrostatic interactions between Zn-ions and structure lattice. This work addresses the strategy of pre-inserting guest materials to vanadium oxide cathode using different intercalants. To achieve this goal, the small organic dye molecules, methyl orange (MO), and methylene blue (MB) are proposed as the intercalants for vanadium oxygen hydrate (VOH). It has been demonstrated that use of these intercalants can facilitate reaction kinetics between Zn²⁺ and VOH, leading to an improvement of specific capacity (293 mAh g^-1 at 0.3 A g^-1 for MO-VOH and 311 mAh g^-1 for MB-VOH) compared to VOH, a large enhancement of excellent energy density (237.1 Wh kg^-1 for MO-VOH, 232.3 Wh kg^-1 for MB-VOH), and a prolong lifespan operation at 3 A g^-1 . The mechanism studies suggest that the weakened electrostatic interactions between the Zn-ions and V-O lattice after intercalating organic molecules contribute to boosting the electrochemical performance of AZIBs unveiled by charge density difference and binding energy.