Structure regulation of O3-type layered cathode materials enables high-capacity and long-cycling sodium-ion batteries

The O3-NaNi_1/3Fe_1/3Mn_1/3O₂, despite its cost-effectiveness and reliable specific capacity, suffers from rapid capacity decay and sluggish Na⁺ diffusion kinetics induced by undesirable phase transitions. To address these limitations, we proposed a Zn/Ti co-doping strategy to synthesize Na(Ni_1/3Fe_1/3Mn_1/3)_0.95Zn_0.025Ti_0.025O₂ (NFMZT) via a straightforward solid-state reaction, which solves the structural instability while maintaining its inherent high-capacity characteristics. Comprehensive experimental investigations coupled with theoretical calculations demonstrate that Zn/Ti co-doping successfully delays the O3 → P3 phase transition, mitigates Jahn-Teller distortion, and boosts electrochemical activity through reduction of the Ni valence state. Consequently, the optimized NFMZT cathode presents excellent reversible capacity of 141.4 mAh g^-1 at 0.1C and demonstrates outstanding cycling stability, retaining 80.0 % of initial capacity after 400 cycles at 1C. Remarkably, the material exhibits superior rate capability, achieving a high specific capacity of 101.0 mAh g^-1 at 5C, outperforming the pristine material. In addition, full-cell tests further validate the practical applicability, with specific capacities of 149.2/104.2 mAh g^-1 at 0.1/5C, respectively. These findings provide fundamental insights for exploiting advanced cathode materials through rational local structure engineering for sodium-ion battery applications.