Fluorine-substituted O3-type NaNi0.4Mn0.25Ti0.3Co0.05O2−F cathode with improved rate capability and cyclic stability for sodium-ion storage at high voltage

O3-type NaNiO2-based cathode materials undergo irreversible phase transition and serious capacity decay at high voltage above 4.0 V in sodium-ion batteries. To address these challenges, effects of F-substitution on the structure and electrochemical performance of NaNi0.4Mn0.25Ti0.3Co0.05O2 are investigated in this article. The F-substitution leads to expanding of interlayer, which can enhance the mobility of Na+. NaNi0.4Mn0.25Ti0.3Co0.05O1.92F0.08 (NMTC-F0.08) with the optimal F-substitution degree exhibits much improved rate capability and cyclic stability. It delivers reversible capacities of 177 and 97 mAh g−1 at 0.05 and 5 C within 2.0–4.4 V, respectively. Galvanostatic intermittent titration technique verifies faster kinetics of Na+ diffusion in NMTC-F0.08. And in-situ XRD investigation reveals the phase evolution of NMTC-F0.08, indicating enhanced structural stability results from F-substitution. This study may shed light on the development of high performance cathode materials for sodium-ion storage at high voltage.