Unexpected Role of Vanadium Dissolution in Activating Anion Redox Chemistry in Aqueous Zn–V 2 O 5 Batteries

Vanadium dissolution in vanadium oxide cathodes for aqueous zinc-ion batteries is widely believed to deteriorate structural stability, yet its potential advantages remain unexplored. Herein, we unravel the unexpected role of mild V-dissolution in activating oxygen redox chemistry in aqueous Zn–V2O5 batteries. The tailored Al3+ preintercalated V2O5 (AlVO) nanobelts experience moderate V-dissolution in the weakly acidic aqueous electrolyte after soaking for 36h, reducing the oxygen coordination number from V3–O to V2–O configurations that create nonbonding O 2p states to trigger the oxygen redox activity. Meanwhile, the interlayer “Al3+-pillars” stabilize the layered structure, expand the interlayer spacing for facile ion-diffusion, and suppress oxygen loss through Al–O bonding. The reversible oxygen redox with CF3SO3– (from the electrolyte) insertion/extraction and vanadium redox with Li+/Zn2+ uptake/release are elucidated by systematic synchrotron, spectroscopic, and imaging characterizations and theoretical computations. Consequently, the AlVO cathode delivers a high discharge capacity (548.9 mAh g–1) and a commendable cycling stability (1800 cycles).