Tailoring Local Chemistry of O3-Type Ni/Fe/Mn-Based Layered Oxide Cathodes for High-Performance Sodium-Ion Batteries

The promising development potential of sodium-ion batteries (SIBs) as complementary candidates to lithium-ion batteries (LIBs) for large-scale energy storage systems calls for a more fundamental investigation and performance optimization of layered transition metal (TM) oxide cathode materials. However, insufficient rate capability and rapid capacity decay have hindered the potential application of low-cost O3-type Ni/Fe/Mn-based layered oxides. Herein, a universal strategy using the multifunctional rare earth elements (REs = Lu, Yb, Er, etc.) as cationic dopants for NaNi_1/3Fe_1/3Mn_1/3O₂ cathodes to manipulate the intrinsic local chemical environment has been successfully reported, which effectively stabilizes the structural framework and improves the Na⁺ ion transport kinetics, owing to the reinforced TM–O bonds, the weakened Na–O bonds, and the more favorable chemical states of Ni and Mn. As expected, such a RE-doping strategy based on tailoring local chemistry allows for an electrochemical performance improvement. The designed Lu-modified NaNi_1/3Fe_1/3Mn_1/3O₂ cathode exhibits a high capacity of 151.36 mA h g^–1 at 0.1 C, excellent rate capability (119.06 mA h g^–1 with a 78.66% retention at 10 C), and a long-term cycling performance with a capacity retention of 82.39% after 500 cycles even at 5 C. The full cell with a hard carbon anode demonstrates a high energy density of 281.3 W h kg^–1 and a long-term cycling performance over 500 cycles at 5 C. This work will demonstrate the role of REs in strategically tailoring the local chemistry of layered oxide cathode materials, boosting the rapid and qualitative development of high-performance SIBs.