Lattice Engineered P2-Type Cathodes with Enhanced Phase-Transition Reversibility and Diffusion Kinetics for High-Power Na-Ion Batteries

P2-type Na 0.67 Ni 0.33 Mn 0.67 O 2 has emerged as a promising cathode material for sodium-ion batteries (SIBs) owing to its high operating voltage (>3.5 V) and considerable theoretical capacity (∼173 mAh g –1 ). Nevertheless, its practical performance is largely hindered by sluggish Na + kinetics, primarily originating from Na + /vacancy ordering and an irreversible P2–O2 phase transition upon deep desodiation. In this work, a dual-doping strategy is employed to develop Na 0.67 Mg 0.05 Ni 0.28 Mn 0.57 Ti 0.1 O 2 (TiMg-P2O), in which Ti 4+ substitution in the transition metal layer stabilizes the oxygen sublattice via strong Ti–O covalent bonding, effectively suppressing lattice oxygen instability and Na + /vacancy rearrangement. Meanwhile, the incorporation of Mg 2+ in both the transition metal (TM) and sodium (Na) layers, with Mg in the sodium layer acting as a structural “pillar”, maintains the interlayer spacing and preserves the stability of fast Na + diffusion pathways even in a deeply desodiated state. As a result, the TiMg-P2O cathode delivers a reversible capacity of 107 mAh g –1 at 1C and retains 97 mAh g –1 at 5C, significantly outperforming the pristine P2O cathode (76 mAh g –1 and 22 mAh g –1 ). This study highlights a practical and scalable codoping strategy to engineer robust P2-type layered oxides with enhanced electrochemical performance for next-generation SIBs.