Internal Vanadium Doping and External Modification Design of P2‐Type Layered Mn‐Based Oxides as Competitive Cathodes toward Sodium‐Ion Batteries

Abstract P2‐type layered manganese‐based oxides have attracted considerable interest as economical, cathode materials with high energy density for sodium‐ion batteries (SIBs). Despite their potential, these materials still face challenges related to sluggish kinetics and structural instability. In this study, a composite cathode material, Na 0.67 Ni 0.23 Mn 0.67 V 0.1 O 2 @Na 3 V 2 O 2 (PO 4 ) 2 F was developed by surface‐coating P2‐type Na 0.67 Ni 0.23 Mn 0.67 V 0.1 O 2 with a thin layer of Na 3 V 2 O 2 (PO 4 ) 2 F to enhance both the electrochemical sodium storage and material air stability. The optimized Na 0.67 Ni 0.23 Mn 0.67 V 0.1 O 2 @5wt %Na 3 V 2 O 2 (PO 4 ) 2 F exhibited a high discharge capacity of 176 mA h g −1 within the 1.5‐4.1 V range at a low current density of 17 mA g −1 . At an increased current density of 850 mA g −1 within the same voltage window, it still delivered a substantial initial discharge capacity of 112 mAh g −1 . These findings validate the significant enhancement of ion diffusion capabilities and rate performance in the P2‐type Na 0.67 Ni 0.33 Mn 0.67 O 2 material conferred by the composite cathode.