Regulation of Local Chemistry in O3-type Layered Oxide Cathodes for Practical Sodium-Ion Batteries

Abstract

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) ions 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 TMn+ dissolution. Consequently, NaNi0.25Fe0.14Mn0.3Li0.1Ti0.15Cu0.03Zn0.03O1.94F0.06 (HEO) delivers a high specific capacity of 152.27 mAh 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.