Probing the Sodium Insertion/Extraction Mechanism in a Layered NaVO₃ Anode Material

For the realization of sodium-ion batteries (SIBs), high-performance anode materials are urgently required with the advantages of being low-cost and environment-friendly. In this work, layered-type NaVO₃ is prepared by the simple solid-state route with a rod-like morphology and used as an anode material for SIBs. The NaVO₃ electrode exhibits a high specific capacity of 196 mA h g^-1 during the first cycle and retains a capacity of 125 mA h g^-1 at the 80th cycle with a high Coulombic efficiency of >99%, demonstrating high reversibility. The sodium diffusion coefficient in NaVO₃ is measured using electrochemical impedance spectroscopy (1.368 × 10^-15 cm² s^-1), the galvanostatic intermittent titration technique (1.15715 × 10^-13 cm² s^-1), and cyclic voltammetry (2.7935 × 10^-16 cm² s^-1). Furthermore, the reaction mechanism during the sodiation/desodiation process is investigated using in situ X-ray diffraction and X-ray absorption near the edge structure analysis, which suggests the formation of an amorphous-like phase and reversible redox reaction of V⁴⁺ ↔ V⁵⁺, respectively.