Lanthanum‐Induced Phase Engineering Enables Enhanced Structural Stability and Fast Na+ Transport in P2/O3 Layered Cathodes for Sodium‐Ion Batteries

Abstract Fe/Mn‐based P2‐type layered oxides are promising cathodes for sodium‐ion batteries (SIBs), yet suffer from poor cycling stability due to Jahn–Teller distortion of Mn 3+ and irreversible P2–Z phase transitions. In this study, a multi‐element doping strategy involving Cu, Mg, and La is employed to construct a structurally stable P2/O3 composite, Na 0.67 Fe 0.19 Mn 0.5 Cu 0.2 Mg 0.1 La 0.01 O 2 (FMCML), via a sol–gel method and high‐temperature calcination. The synergistic doping suppresses Mn 3+ redox activity, mitigates lattice distortion, and enhances Na + diffusion kinetics. Notably, La 3+ incorporation induces LaO 6 octahedral formation, which refines particle size and boosts crystallinity. As a result, FMCML exhibits outstanding rate performance and long‐term durability, with capacity retentions of 99.11%, 87.21%, and 74.92% after 100, 300, and 1600 cycles at 200, 1000, and 2000 mA·g −1 , respectively. The dual‐phase structure promotes structural reversibility, suppresses Na + /vacancy ordering, and enhances ambient air stability. This work offers a practical approach to designing robust layered oxide cathodes through rational phase and composition engineering, paving the way for next‐generation high‐performance SIBs.