Enhancing vanadium pentoxide-based (V₂O₅) cathodes for high-performance aqueous zinc-ion batteries: optimization of interlayer spacing, ion kinetics, voltage window

The urgent need for safe, affordable, and environmentally responsible energy storage has placed rechargeable aqueous zinc-ion batteries (AZIBs) at the centre of next-generation research. While earlier reviews surveyed V2O5 cathodes in broad terms, none has yet unified the latest insights on interlayer engineering, electrolyte coordination, and operando diagnostics into a coherent design framework. Focusing on progress from 2019 to mid-2025, this review offers three distinctive contributions. First, it correlates the crystallographic evolution of V2O5, captured by synchrotron X-ray, in situ TEM, and Raman studies, with voltage plateaus and capacity decay, providing a mechanistic map of Zn2+/H2O co-intercalation and phase transitions. Second, it compares emerging synthesis routes (sol-gel, hydrothermal, solid-state, and electrochemical deposition) through a quantitative lens, linking specific surface area, defect chemistry, and conductivity (10-2 to 10-1 S cm-1) to rate capability and long-term retention. Third, it surveys interlayer-expansion strategies, metal-ion pre-intercalation, organic pillar insertion, conductive-polymer hybrids, and hierarchical nanostructuring, showing how each modulates Zn2+ diffusivity, lattice strain (<5% with water co-insertion), and dissolution resistance. By integrating experimental advances with density-functional-theory, ab initio molecular-dynamics, and machine-learning predictions, the review distils actionable design principles and a forward roadmap for achieving >400 mAh g-1 capacities and >90% retention beyond 2000 cycles. These new perspectives position V2O5 not merely as a promising cathode, but as a model system for understanding and optimizing layered hosts in aqueous multivalent batteries.