Abstract <p>Due to their high specific capacities and favorable average operating voltages, P2-type and O₃-type layered oxides were used as commercial cathode materials for sodium-ion batteries. While P2-type oxides exhibited superior air stability compared to their O₃ counterparts, they suffered from lower sodium stoichiometry and poor cycle stability, primarily due to high-voltage phase transitions. To address these limitations, the study investigated the effects of tin (Sn) doping on the structural and electrochemical properties of P2-type Na_0.67Ni_0.33Mn_0.67O₂. Specifically, 6% of the Ni²⁺ ions were substituted with more electronegative Sn⁴⁺ ions, which led to an expansion of the sodium polyhedra and an increase in Na–O bond lengths, effectively enlarging the diffusion pathways for Na⁺ ions. The higher electron density introduced in the transition metal–oxygen (TM–O) layers also generated interlayer repulsion, further expanding the Na–O trigonal prisms. These structural modifications enhanced Na⁺ ion kinetics and significantly improved high-rate battery performance. The doped composition, Na_0.67Ni_0.33Sn_0.02Mn_0.67O₂, delivered a discharge capacity of 66 mAh g⁻¹ at a 5&#xa0;C rate and retained 84.6% of its capacity after 300 cycles in a half-cell configuration. In full-cell testing, the material achieved a capacity of 53 mAh g⁻¹ with 40.6% retention after 50 cycles and a high energy density of 218 Wh kg⁻¹.</p> Graphical abstract <p></p>