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

P2-type Na0.67Ni0.33Mn0.67O2 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 Na0.67Mg0.05Ni0.28Mn0.57Ti0.1O2 (TiMg-P2O), in which Ti4+ 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 Mg2+ 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.