Oxygen Vacancy-Driven Anion Gating for High-Voltage Asymmetric Zinc-Air Batteries

Abstract

Rechargeable zinc-air batteries (ZABs) are promising for next-generation energy storage, yet their output voltage is strongly constrained by conventional electrolyte configurations. Although pH-decoupled asymmetric systems can expand the electrochemical window, uncontrolled OH– crossover progressively dissipates the interfacial pH gradient and accelerates neutralization, leading to rapid performance decay. Here, an oxygen vacancy-driven anion gating (OVDAG) strategy is reported for asymmetric ZABs using a separator modified with oxygen-vacancy-rich WO3 nanofillers. The oxygen-vacancy-rich WO3 introduces defect-associated W sites that modulate the interaction with OH– and effectively retard OH– crossover across the asymmetric interface. This vacancy-mediated anion regulation suppresses interfacial neutralization, stabilizes the local pH gradient, and enhances ionic conductivity by 72%, thereby alleviating the trade-off between ion selectivity and transport efficiency. As a result, the assembled asymmetric ZABs deliver open-circuit voltages of 2.16 V (liquid) and 2.22 V (gel), stable discharge plateaus of ∼1.7–1.8 V and cycling durability of up to 150 h (liquid) and 120 h (gel). This work establishes oxygen-vacancy-driven anion gating as an effective strategy for high-voltage and durable ZABs.