Rare earth Ce-modulated polyoxometalate intercalation into V2O5: defect engineering and electronic regulation toward aqueous zinc-ion batteries.

Aqueous zinc-ion batteries (AZIBs) are promising candidates for large-scale energy storage due to their high safety, low cost and environmental benignity. However, vanadium oxide (V2O5) cathodes are limited by Zn2+ diffusion kinetics, structural collapse during cycling, and insufficient active sites. Polyoxometalates (POMs) are inorganic clusters with tunable electronic structures that can be used for electrode modification. Herein, a one-pot hydrothermal method is employed to intercalate rare-earth cerium-modified molybdenum-based polyoxometalate (CeMo7) into vanadium pentoxide interlayers to obtain cerium‑molybdenum polyoxometalate intercalated with vanadium oxide precursor (CMVO). Combined with a synergistic modification strategy via heat treatment, the targeted cathode material (CMVO-400, CMVO calcined at 400 °C) with a fluffy porous agglomerated structure is successfully fabricated. CeMo7 intercalation widens the V2O5 interlayer spacing, defects and active sites are introduced, and vanadium local electronic states are modulated. With the heat treatment process, the porous structure is optimized, electrolyte wettability is significantly improved and Zn2+ transport is accelerated. The CMVO-400 exhibits excellent cycling stability and rate capability, with a capacity retention of 71.4% after 1500 cycles at 4.0 A g-1 and a specific capacity of 413.1 mAh g-1at 0.3 A g-1. In-situ and ex-situ characterization techniques reveal the Zn2+/H+ co-intercalation storage mechanism during charge and discharge. By proposing a synergistic modification strategy for vanadium-based cathodes, this work provides new insight into the development of advanced electrode materials for AZIBs.