This study demonstrates that coating the sodium-ion battery (SIB) material Na₃V₂(PO₄)₃ (NVP) with a thin layer of niobium oxide (Nb₂O₅) dramatically improves its efficiency, lifespan, and safety. These improvements have significant energy and environmental implications. SIBs are a promising alternative to lithium-ion technology because sodium is far more abundant and inexpensive. NVP is attractive for SIBs due to its stable structure and good ion conductivity, but its rate capability and cycling stability are limited by slow charge transfer and interfacial degradation. The authors synthesized NVP/C via a citric-acid sol–gel method and applied 1–5 wt% Nb₂O₅ coatings using a simple impregnation process. Structural and spectroscopic analyses (XRD, TEM, Raman, XPS) confirmed uniform Nb₂O₅ coatings without altering NVP’s crystallinity. Electrochemical testing showed that the 3 wt% Nb₂O₅ coating achieved the best balance of capacity, rate performance, and cycling life, maintaining 97% capacity after 300 cycles and an energy density of 307 Wh kg⁻¹. The Nb₂O₅ layer reduced charge-transfer resistance, enhanced surface capacitance, and acted as a hydrofluoric acid (HF) scavenger—forming NbF₅ at the interface, which improved stability. Even under −15 °C to 60 °C, coated electrodes maintained over 90% of their initial capacity. Overall, Nb₂O₅ surface modification effectively enhances the kinetics, durability, and safety of NVP cathodes, offering a practical route toward high-performance, low-cost sodium-ion batteries. This work entitled “Unlocking the performance of sodium-ion batteries by coating Na₃V₂(PO₄)₃ with Nb₂O₅” was published on Acta Physico-Chimica Sinica (published on September 9, 2025).
DOI:

10.1016/j.actphy.2025.100180