NASICON-Na(NbO2)2PO4 anode material with high capacity and good stability for sodium-ion batteries

Niobium-based phosphates have the advantages of high stability and environmental protection and have good application prospects in sodium-ion batteries. The pure phase of Na(NbO₂)₂PO₄ (NNP) powder was successfully synthesized by different methods in this work, and the materials were characterized via XRD, XPS, SEM, and electrochemical methods. At the current density of 100 mA g⁻¹, the discharge-specific capacity of NNP is 521.8 mAh g⁻¹ in the first cycle and remains at 462.4 mAh g⁻¹ after 200 cycles, indicating that it has good cycling stability. The kinetic results obtained from cyclic voltammetry (CV) show the pseudo-capacitance contribution accounts for a large percentage of the capacity. The charge transfer resistance of NNP is 260.3 Ω, which is significantly smaller than the others derived from electrochemical impedance spectroscopy (EIS). These pointed to the advantages of NNP in anode material for SIBs.