High-Performance NaVO₃ with Mixed Cationic and Anionic Redox Reactions for Na-Ion Battery Applications

Sodium-ion batteries (NIBs) are a potential low-cost alternative to lithium-ion batteries for large-scale energy storage, but many high-capacity NIB cathode materials undergo irreversible structural changes during charge and discharge, leading to fast capacity fading. Herein, monoclinic NaVO3 exhibits good cycle performance with high capacity as a cathode material for NIBs. In situ synchrotron X-ray diffraction studies show that the material structure is virtually invariant during Na+ (de-)intercalation, with the a and b lattice parameters changing only by 0.13 and 0.19%, respectively. The material undergoes an oxygen redox reaction during initial charge while delivering a remarkable specific capacity of 245 mAh g–1 (1.2–4.7 V) with contributions from cationic (V4+/V5+) and anionic (O2–/O–) redox couples during discharge. The stable VO4 tetrahedral framework also enables the material to give superior rate and cycle capabilities, with a capacity of 164 mAh g–1 (67% utilization) at a current of 1000 mA g–1 (about 5C) and a capacity retention of 90% after 50 cycles. Density functional theory calculations further verify the stability of the material and the charge–discharge mechanism. This work can broaden the horizon for designing high-energy cathode materials with enhanced structural stability for sodium-ion batteries.