Oxygen Vacancy Engineering and Pre-accommodated Distortion Stabilization Enabling Superior Rate and Cycling Performance in P2-Type Mn-Rich Cathodes.

P2-type layered oxides have been considered as an ideal cathode material for sodium-ion batteries (SIBs) due to their high capacity and facile synthesis, yet their practical application is severely hampered by Jahn-Teller distortion, manganese dissolution, and poor intrinsic ionic conductivity. While conventional cation doping strategies can partially mitigate these issues, the complex mechanisms and multi-component interactions pose challenges for rational material design. Here, we propose an oxygen vacancy engineering strategy, introducing controllable oxygen vacancies into Na0.67Ni0.15Fe0.2Mn0.65O2 (NFM) by regulating the calcination atmosphere. The introduced oxygen vacancies effectively modulate the local electronic structure of manganese, lower its average valence state, and induce the formation of an orthorhombic P'2 phase. Attributed to the pre-accommodating lattice distortion of the P'2 phase, the structural stability and reversibility of NFM are significantly enhanced. Concurrently, the increased cationic disorder improves both electronic and ionic conductivity. Benefiting from these synergistic effects, the modified NFM cathode delivers outstanding rate and cyclability performance, maintaining a considerable capacity of 127.3 mAh g-1 at 5 C and a high capacity retention of 90.8% even after 500 cycles. This work not only creates an effective vacancy engineering approach to simultaneously enhance the rate capability and cycling stability of Mn-rich cathodes but also provides guidance for designing high-performance electrode materials for SIBs via anion framework regulation.