Structural Stabilization and Superior Electrochemical Performance of Yttrium-Doped O3-NaFe0.4Ni0.3Mn0.3O2 Cathodes for Sodium-Ion Batteries

This is the first demonstration of successful Y3+ doping, and Y3+-doped O3-NaFe0.4Ni0.3Mn0.3O2 (NaFNM) cathodes exhibit superior cyclability and C-rate capabilities. Y3+ doping enabled cells with 91% capacity retention at 1 C after 100 cycles and a high specific capacity of 102 mA h g–1 at a 7 C rate. Furthermore, the full cell delivered outstanding cycling stability, with a capacity retention of 80% after 500 cycles at 1 C and 71.3% after 1000 cycles. Operando X-ray diffraction spectroscopy (XRD) and X-ray absorption spectroscopy, along with simulations using density functional theory and neural network potential methods, provided comprehensive insights on the effects of Y3+ doping on the cycling characteristics. Our results confirm that Y3+ doping effectively stabilizes the O3 structure, enhances the electrochemical performance, and addresses the challenge of irreversible O3 to P3 phase transitions.