Synergistic Stabilization of Anionic-Cationic Dual Frameworks via Mg Doping and O2-Type Structure Construction in Lithium-Rich Cathodes

Lithium-rich manganese-based cathode materials (LRMOs) have high specific capacity (>250 mAh g–1) and low cost. However, their commercial viability is plagued by irreversible oxygen release, transition metal migration, and structural degradation (layered-to-spinel/rock-salt phase transitions) during cycling, leading to rapid capacity fading and severe voltage decay. Herein, departing from conventional single-modification routes, we propose a strategy of synergistically regulating O2-type layered structure and Mg doping, to enhance structural stability by constructing a robust anion–cation dual framework. Specifically, the ABAC stacking in the O2-type structure stabilizes the anionic framework by suppressing lattice oxygen release, while Mg doping stabilizes the local transition metal environment and mitigates cation migration and lattice distortion, achieving synergistic stabilization of both frameworks. Structural characterizations confirm that Mg introduction optimizes particle morphology and valence state distribution. The optimized O2–Mg–NCM delivers an initial Coulombic efficiency of 98.51%, a capacity retention of 86.6% after 200 cycles, and a mere voltage decay of 0.178 V after 100 cycles. It exhibits superior reaction kinetics, with a charge transfer resistance of 39.08 Ω and Li+ diffusion coefficient of 2.94 × 10–15 cm2 s–1. CV, dQ/dV, and EIS analyses further demonstrate that the synergy between the O2 structure and Mg doping enhances anionic redox reversibility and alleviates structural degradation, improving cycling stability and voltage retention of LRMOs. This study elucidates the dual-framework synergistic stabilization mechanism, providing new insights into designing highly stable, high-energy-density LRMOs.