ABSTRACT O3‐type layered oxides are key materials for achieving high‐energy‐density sodium‐ion batteries (SIBs). However, their irreversible phase transitions, oxygen loss, and interface degradation at high voltages (>4.0 V) lead to rapid capacity fading. In this work, using O3‐Na 0.9 Ni 0.22 Fe 0.3 Mn 0.48 O 2 (NFM) as the base material, a stable structural framework and efficient ion channels were constructed through a Li + /Ti 4+ dual‐doping strategy. The dual‐doped Na 0.9 Ni 0.22 Li 0.1 Fe 0.2 Ti 0.1 Mn 0.38 O 2 (NLFTM) material exhibited significantly improved specific capacity and rate performance in the voltage range of 2.0–4.3 V. It delivered a reversible capacity of 180.7 mAh/g at 0.1 C and maintained a capacity of 91.1 mAh/g even at a high rate of 10 C. Furthermore, after 100 cycles at 1 C, NLFTM retained 83% of its capacity, markedly outperforming the pristine NFM (56.6%). Ex situ XRD results confirmed that dual‐doping enhanced the reversibility of the O3↔P3 phase transition during charge/discharge, thereby ensuring structural stability during high‐voltage cycling. XPS analysis revealed that the dual‐doping strategy successfully inhibited irreversible oxygen loss, breaking the detrimental cycle of “oxygen release–structural collapse–capacity decay” at high voltage. The EIS, GITT, and CV test results demonstrated that the synergistic effect of dual‐doping effectively enhanced charge transfer and improved Na + diffusion kinetics.
Tian et al. (Fri,) studied this question.