Enhanced electrochemical performance of pre-treated V₂O₅ as cathode material in aqueous Zinc-ion batteries

The evolution of cathode materials is crucial for the large-scale manufacturing of aqueous zinc-ion batteries. Vanadium-based materials possess large interlayer distances and thus allow for easy intercalation/deintercalation processes of zinc ions. However, commercially available V₂O₅ is seldom used directly as cathode materials for aqueous zinc ion batteries because of low activity and more side reactions. Here, we have outlined a methodology to to enhance its reactivity and prevent the side reaction effectively. The pre-treated V₂O₅ (V₂O₅-P) was carried out through a combination of water bath treatment at a temperature of 65℃ and freeze-drying, which showed expanded layer spacing and increased density of active sites. The structural variations of V₂O₅ during pretreatment were analyzed using various test methods, and the structural evolution in cathode material and energy storage mechanism during charge/discharge was also investigated by in-situ Electrochemical Impedance Spectroscopy. The V₂O₅-P material showed almost no capacity degradation during 200 charge/discharge cycles (0.5 A g⁻¹) with a Coulombic efficiency consistently exceeding 99.98 %. After 5000 cycles (2 A g⁻¹), V₂O₅-P maintained 70 % specific capacity with a Coulombic efficiency of more than 99.5 %. As a result, this work presented an easy-to-use method for commercialized materials applied to energy storage on a larger scale.