Ti SubstitutionStrategy Improves ElectrochemicalPerformance of Na₃V₂(PO₄)₂F₃ Cathode

Abstract

NASICON-type Na₃V₂(PO₄)₂F₃ (NVPF) is a promising cathode for sodium-ion batteries (SIBs), but its performance is hindered by Na₃V₂(PO₄)₃ (NVP) impurities and intrinsic limitations. To overcome these challenges, Ti-substituted NVPF cathodes are successfully synthesized using the sol–gel method in this study. Theoretical calculations and advanced analyses confirm that substituting Ti ions for V in the NVPF lattice effectively eliminates NVP impurities, mitigates the low-voltage plateau issue, and enhances both electronic conductivity and sodium-ion diffusion kinetics. Hence, the optimized Na₃V₁.₉₅Ti₀.₀₅(PO₄)₂F₃ cathode demonstrated a high initial capacity of 129.10 mAh g^–1 at 0.2 C. Notably, it exhibited excellent cycling stability, with capacity retentions of 91.98% after 500 cycles at 5 C and 81.14% after 6000 cycles at 30 C, significantly outperforming the unsubstituted NVPF sample. This study provides a practical new approach for the development of high-performance cathode materials for SIBs and is expected to accelerate the commercialization process of SIBs.