Vanadium Oxide Nanoflowers Regulated by Na+/Ga3+ Preinsertion and Defect Engineering for Zinc-Ion Batteries

Abstract

Vanadium-based oxides, with abundant valence states and excellent theoretical specific capacity, are among the most promising cathode materials for aqueous zinc-ion batteries (ZIBs). However, their practical applications are still limited by considerable challenges, including low intrinsic conductivity and structural instability during cycling. In light of this, we propose a modification strategy combining Na+/Ga3+ preinsertion with argon phosphating. Na+/Ga3+ serve as structural “pillars” between the layers, widening the interlayer spacing and thereby stabilizing the architecture while collaboratively inducing a profound morphological reconstruction at the nanoscale. This transforms the material from disordered bulk agglomerates into intricate three-dimensional hierarchical nanoflowers assembled by ultrathin nanosheets. This unique nanoscale architecture effectively shortens ion diffusion distances and provides a high density of active sites for Zn2+ storage. The kinetic pinning effect generated during the argon phosphating process effectively suppresses the transformation of the material into the tunnel-like NaV6O15 phase, locking the material in a metastable layered V2O5 phase rich in oxygen vacancies and exhibiting high capacity. Benefiting from optimized microstructure and defect engineering, the VO-NaGaP achieves a high discharge specific capacity of 481.85 mAh g–1 at 0.2 A g–1 and retains 84.27% of its initial capacity after 3000 cycles at 5 A g–1. The unmodified HVO-Na0Ga0 exhibits a discharge specific capacity of only 321.10 mAh g–1 at 0.2 A g–1, and after 3000 cycles at 5 A g–1, the capacity retention rate is only 79.5%. This work reveals the crucial role of ion preintercalation in stabilizing the structure of vanadium-based cathode materials and the key mechanisms of gas-phase phosphating in defect creation and crystal phase regulation, providing a reference for developing high-energy-density and long-life cathode materials for zinc-ion batteries.