Regulating Phase Stability of O3-Type-Layered Oxide Cathode via Zn2+ Substitution

O3-type-layered oxides have gained recognition as highly promising cathode materials for rechargeable sodium-ion batteries, offering superior cyclical sodium compatibility, higher theoretical capacity, and desirable initial Coulombic efficiency than their P2-type counterparts. However, their practical utilizations are often impeded by inherent structural instability and irreversible O3–P3 phase transition, leading to rapid capacity deterioration and limited lifespan. In this study, a transition cation (Zn2+)-doped O3-type Na[Zn0.05(Ni1/3Fe1/3Mn1/3)0.95]O2 (Zn0.05-NNFMO) was synthesized via a facile sol–gel method, which demonstrated a high reversible capacity of 116.3 mA h g–1 with superior capacity retention. The expanded interplanar space of Zn0.05-NNFMO enhances the Na+ diffusion kinetics and reduces the charge-transfer resistance. Moreover, Zn2+ doping significantly mitigates irreversible phase transitions and lattice distortion caused by the Jahn–Teller effect, thereby contributing to improved structural stability and longevity. This study provides a feasible strategy for constructing stabilized O3-type-layered oxides and high-performance sodium-ion batteries.