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

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_0.67Ni_0.23Mn_0.67V_0.1O₂@Na₃V₂O₂(PO₄)₂F was developed by surface-coating P2-type Na_0.67Ni_0.23Mn_0.67V_0.1O₂ with a thin layer of Na₃V₂O₂(PO₄)₂F to enhance both the electrochemical sodium storage and material air stability. The optimized Na_0.67Ni_0.23Mn_0.67V_0.1O₂@5wt %Na₃V₂O₂(PO₄)₂F 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_0.67Ni_0.33Mn_0.67O₂ material conferred by the composite cathode.