Unlocking bulk-phase stagewise activation in vanadium oxide via water regulation for high-rate Zn-ion batteries

Electrochemical activation (ECA) represents a powerful approach to unlock the high-capacity potential of vanadium oxide cathodes for aqueous zinc-ion batteries (AZIBs). The role of water in ECA extends beyond surface reactions, yet its underlying bulk-phase activation mechanisms remain largely unexplored. This work uncovers a previously overlooked stagewise ECA process regulated by the bulk-phase water penetration, involving concentrated oxidation and subsequent hydrolysis-induced phase transformation. Through a synergistic dual-ion engineering strategy, a model NaAl-VO 2 nanoflower precursor is constructed, where Al 3+ and Na + cooperatively tailor the morphology and (001) layer spacing. This design unlocks deep water reaction in VO 2 , triggering a pore-forming cascade reaction fundamentally distinct from traditional surface-limited activation. The bulk reaction mechanism facilitates rapid formation of highly active NaAl-H x V 2 O 5 nanonetworks, leading to a high specific capacity (571.3 mA h g −1 at 0.1 A g −1 ) and enhanced rate performance (239.5 mA h g −1 after 10,500 cycles at 20 A g −1 ). Ion-synergized regulation of water reaction depth can serve as a universal strategy for developing high-performance electrodes in aqueous electrolyte batteries.