Vacancy‐Engineered Vanadium Cathode for Fast‐Charging Aqueous Zinc Batteries of Ultra‐Long Cycle Life
Saheb Bag, Vikas Singh Thakur, Abhirup Bhadra, Swastika Banerjee, Dipan Kundu, C. Retna Raj
Abstract
Abstract Aqueous zinc‐ion batteries have emerged as strong contenders for sustainable energy storage; however, their widespread adoption is constrained by sluggish Zn 2+ transport and suboptimal cathode performance. A rapid, energy‐efficient solvothermal synthesis of Na 2 V 6 O 16 is reported, and introduces cation vacancies via initial electrochemical engineering. This electrochemical pre‐treatment generates Na⁺ vacancies, significantly enhances Zn 2+ diffusion, and enables synergistic Zn 2+ /H + co‐storage. Ex situ and operando analyses, supported by theoretical and computational studies, confirm the pivotal role of Na⁺ vacancies in facilitating ion transport and improving capacity. The vacancy‐engineered cathode exhibits a high discharge capacity of 692.8 mAh g −1 at 100 mA g −1 , delivering an energy density of 467.6 Wh kg −1 and outstanding cycling stability over 10 000 cycles at 10 A g −1 . It also sustains a capacity of 366.6 mAh g −1 at 1000 mA g −1 and retains 395.2 mAh g −1 at 100 mA g −1 under high mass loading, highlighting its rate capability and practical applicability. The battery shows fast‐charging capability, delivering a specific capacity of 138.2 mAh g −1 within 12.4 s, and has an ultra‐long cycle life of over 75 000 cycles with capacity loss of only 0.0003% per cycle at a current density of 40 A g −1 .