Oxygen Vacancy Engineering of Ultrafine ZnAl 2 O 4 Nanoparticles as a Robust Protective Layer for Dendrite‐Free and Long‐Lifespan Aqueous Zn Metal Anodes

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) hold great promise for safe and sustainable energy storage, but their commercialization is impeded by severe Zn dendrite growth and interfacial instability. To address these challenges, we propose a defect engineering strategy employing ultrafine ZnAl 2 O 4 (ZAO) nanoparticles (∼5 nm) with oxygen vacancy defects as an artificial protective layer for Zn anodes. Synthesized via a scalable coprecipitation approach, the ZAO layer demonstrates exceptional Zn 2+ affinity and rapid ion diffusion, enabling uniform Zn deposition and suppressing parasitic reactions. Remarkably, the ZAO@Zn symmetric cell achieves an unprecedented cycling stability of 3600 h at 20 mA cm −2 , outperforming most reported Zn anodes modified with metal oxyacid compounds. Moreover, the assembled ZAO@Zn//MnO 2 full cell retains a capacity of 166.5 mAh g −1 after 1000 cycles at 2 A g −1 . This work highlights that engineering oxygen vacancies in the ZAO layer is an effective strategy to enhance the performance and longevity of Zn anodes in AZIBs, paving the way for more reliable and efficient energy storage solutions.