Low‐Crystalline Ag 1.2 V 3 O 8 : A Zinc‐Ion Storage Cathode With an Ultrahigh Capacity of 525 mAh g −1 Enabled by Oxygen‐Vacancy‐Rich Coordination Environments

Abstract

ABSTRACT Conventional vanadium‐based cathodes are limited by sluggish Zn 2+ transport, poor electronic conductivity, and incomplete utilization of redox‐active sites. Here, redox‐active Ag serves as a regulator of local coordination chemistry in a short‐range‐ordered low‐crystalline vanadate. Ag incorporation reconstructs the local Ag‐V‐O environment, lowers the oxygen‐vacancy formation energy, promotes V 5+ /V 4+ conversion, and activates electrochemically accessible Ag/V dual‐redox centers, thereby simultaneously enhancing electronic accessibility and Zn 2+ transport kinetics. Meanwhile, the short‐range‐ordered low‐crystalline framework stabilizes these defect‐rich coordination environments, provides pseudocapacitive‐favored charge‐storage pathways, and accommodates local structural strain during repeated Zn 2+ insertion/extraction. Density functional theory (DFT) calculations reveal that Ag incorporation markedly reduces the Zn 2+ migration barrier and increases electronic states near the Fermi level. Consequently, the low‐crystalline silver vanadate cathode delivers an ultrahigh reversible capacity of 525.51 mAh g −1 at 0.1 A g −1 , a high energy density of 499.23 Wh kg −1 , excellent rate capability, and outstanding cycling stability with 96.2% capacity retention after 5,000 cycles at 8 A g −1 . This work demonstrates that local coordination reprogramming unlocks Ag/V redox chemistry and pseudocapacitive Zn 2+ storage, highlighting a promising strategy for enhancing redox accessibility and Zn‐ion storage in low‐crystalline vanadate cathodes.