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.