Dual‐Modification of P2‐Na _0.67 Fe _0.5 Mn _0.5 O ₂ via Sn ⁴⁺ Doping and LiF Coating Toward High‐Performance Sodium‐Ion Batteries

ABSTRACT P2‐Na 0.67 Fe 0.5 Mn 0.5 O 2 (NFMO) cathode material has garnered growing interest for sodium‐ion batteries (SIBs), owing to the high theoretical capacity, environmentally friendly Fe/Mn redox couples, and low cost. However, its practical application is hindered by insufficient capacity delivery and rapid capacity decay originating from the sluggish Na + kinetics and structural degradation. Here, a dual‐modified P2‐NFMO (denoted as Sn‐LiF/NFMO) with Sn 4+ doping and LiF coating is prepared via facile ball milling and calcination to solve the issues. The results reveal that Sn 4+ doping enlarges the Na layer distance and suppresses the internal strain, thus improving Na + diffusion kinetics and inhibiting intergranular cracking. The reinforced Mn‐O bonding effectively alleviates the Jahn‐Teller distortion, significantly suppressing phase transitions. Additionally, the LiF coating helps prevent the dissolution of transition metals and the release of lattice oxygen without impeding charge transport. Consequently, the Sn‐LiF/NFMO‐3% || Na cell delivers a high capacity (193.5 mAh g −1 at 130 mA g −1 ) and remarkable rate capability (84.1 mAh g −1 at 1300 mA g −1 ). After 100 cycles at 260 mA g −1 , Sn‐LiF/NFMO‐3% retains 125.4 mAh g −1 (68% capacity retention), significantly outperforming pristine NFMO (44.6 mAh g −1 , 39% capacity retention). This work offers a viable strategy to develop high‐performance layered cathode materials for SIBs.