Fast and Stable Zinc Storage in an Erbium‐Doped Vanadium Pentoxide Cathode With Electrochemically Reconstructed Hydrate Phase

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) hold promises for the next‐generation grid‐scale electrochemical energy storage. Vanadium pentoxide (V 2 O 5 )‐based materials with high theoretical Zn‐storage capacities are considered a viable choice of cathode, yet they typically suffer from sluggish Zn 2+ diffusion kinetics and inferior electronic conductivity, and require a long electrochemical reconstruction process to be partially converted into a Zn 2+ ‐intercalatable hydrate phase. Here we show that, introduction of 2 mol% erbium (III) cations (Er 3+ , relative to the total metal content) into α ‐V 2 O 5 significantly improves charge transfer kinetics while facilitates thorough structural reconstruction to generate an active Zn 0.25 V 2 O 5 ·H 2 O phase during the initial battery discharge process. The reconstructed phase features an expanded (001) interlayer spacing of 10.75 Å, which not only accelerates Zn 2+ diffusion, but also promotes uniform valance state evolution of vanadium and Zn 2+ (de)intercalation from cathode surface to bulk. Consequently, the Er‐doped α ‐V 2 O 5 (ErVO) cathode demonstrates outstanding Zn storage properties, delivering a reversible capacity of 402 mAh g −1 at 1 A g −1 and 301 mAh g −1 at 10 A g −1 , and a high capacity retention of 82% after 3000 cycles. In this way, we establish rare earth metal doping as an effective strategy for structural engineering and performance optimization of AZIB cathode materials.