Low-Crystalline Ag1.2V3O8: A Zinc-Ion Storage Cathode With an Ultrahigh Capacity of 525 mAh g-1 Enabled by Oxygen-Vacancy-Rich Coordination Environments.

Conventional vanadium-based cathodes are limited by sluggish Zn2+ 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 V5+/V4+ conversion, and activates electrochemically accessible Ag/V dual-redox centers, thereby simultaneously enhancing electronic accessibility and Zn2+ 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 Zn2+ insertion/extraction. Density functional theory (DFT) calculations reveal that Ag incorporation markedly reduces the Zn2+ 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 Zn2+ storage, highlighting a promising strategy for enhancing redox accessibility and Zn-ion storage in low-crystalline vanadate cathodes.