Enhanced Structural Transformation Enabled by Low‐Crystalline Vanadium Oxides in Aqueous Zinc‐Ion Batteries

ABSTRACT Aqueous batteries are gaining attention owing to their high safety and cost‐effectiveness. Among these, Zn‐based aqueous batteries excel because of Zn's low redox potential (−0.76 V vs. SHE), its abundance, and eco‐friendliness. However, despite their advantages, challenges, such as low energy density and limited cycle life limit their usage. This study addresses these issues by employing low‐crystalline V 2 O 4.86 as a cathode material, enhanced with oxygen vacancies created by controlled annealing time. The structure of low‐crystalline V 2 O 4.86 facilitates rapid structural transformation into the highly active phase Zn 3+ x (OH) 2 V 2 O 7 ·2(H 2 O). Electrochemical tests revealed a 22% capacity improvement for low‐crystalline V 2 O 4.86 (360 mAh g −1 ) over high‐crystalline V 2 O 5 (295 mAh g −1 ) at 0.8 A g −1 , attributed to the presence of active oxygen vacancies. Comprehensive structural analysis, spectroscopy, and diffusion path/barrier studies elucidate the underlying mechanisms for the first time, highlighting the potential of oxygen‐engineered V 2 O 5 . These findings indicate that electrodes engineered with oxygen vacancies offer promising insights in advancing cathode materials for high‐performance secondary battery technologies.