• • The synergistic high sodium and Li/Mg co-doping strategy achieves 82.3% capacity retention after 500 cycles at 1C, a 16.9% improvement over the undoped P2-type cathode (65.4%), directly addressing the cycling stability bottleneck for commercial SIBs.
• • The co-doped cathode delivers a reversible capacity of 112 mAh/g at 5C, demonstrating superior rate capability due to the open prismatic Na+ diffusion channels and reduced Na+/vacancy ordering, which is critical for high-power applications.
• • In-situ XRD analysis confirms that the co-doping suppresses detrimental P2-O2 phase transitions during cycling, maintaining structural integrity and reducing volume strain, which is essential for long-term operational reliability.
• • The high sodium content (x > 0.7) elevates the TM(3d-eg*) energy level, lowering the energy barrier for electron extraction and enhancing reaction kinetics, as evidenced by reduced polarization and improved electrochemical performance.