Regulation of local chemistry in O3-type layered oxide cathodes for practical sodium-ion batteries

O3-type layered oxide cathodes have emerged as promising candidates for advanced sodium-ion batteries (SIBs) due to their high theoretical specific capacity. However, undesirable phase transitions, irreversible O₂ release, and transition metal (TM) ion dissolution severely deteriorate their long-cycle stability. Herein, a cation-anion dual-site high-entropy doping strategy is proposed to modulate the local chemistry of O3-type layered oxide cathodes, aiming to enhance the covalency of TM-O bonds. The robust covalent TM-O bonds can effectively suppress adverse phase transitions, inhibit irreversible oxygen redox reactions, and reduce TM ⁿ⁺ dissolution. Consequently, NaNi_0.25Fe_0.14Mn_0.3Li_0.1Ti_0.15Cu_0.03Zn_0.03O_1.94F_0.06 (HEO) delivers a high specific capacity of 152.27 mA h g^-1 and a capacity retention of 73.69% after 500 cycles. More importantly, HEO exhibits impressive temperature tolerance, superior air stability and acceptable full-cell performance, demonstrating its huge potential for practical SIBs application. This work develops a versatile cation-anion dual-site high-entropy doping strategy to modulate the local chemistry of O3-type layered oxide cathodes, furnishing a robust foundation for advancing cathode materials for practical SIBs.