Unlocking the performance of sodium-ion batteries by coating Na3V2(PO4)3 with Nb2O5

Abstract

Na₃V₂(PO₄)₃ (NVP) is a promising cathode material for sodium-ion batteries owing to its NASICON-type framework, which enables efficient reversible sodium insertion. However, its practical performance is limited by slow charge transfer at high cycling rates and cycling instability. Here, we report a facile impregnation method to deposit Nb₂O₅ on NVP particles, aiming to enhance high-rate capability and long-term cycling stability. Structural and spectroscopic analyses (XRD, electron microscopy, Raman, XPS, and X-ray fluorescence spectroscopy) confirm the crystallinity of NVP and the uniform presence of Nb₂O₅ on particle surfaces without compromising sodium reversibility. Electrochemical measurements reveal that Nb₂O₅-coated samples show the highest diffusion coefficients, ensuring superior high-rate performance and cycling stability. The 3 % Nb₂O₅ coating delivers the highest diffusion coefficients, superior cycling stability, and sustained capacity retention at a 1C rate. Cyclic voltammetry and impedance spectroscopy indicate enhanced surface capacitance, facilitating rapid sodium storage. XPS shows the conversion of Nb₂O₅ into NbF₅, resulting from HF scavenging, which improved interfacial stability. Extended cycling tests validate the long-term durability of the coated electrode. These results demonstrate that Nb₂O₅ surface modification is an effective strategy to overcome the intrinsic limitations of NVP, offering a viable route to high-performance sodium-ion batteries.