Tuning Local Electronegativity for Reversible Oxygen Redox in Sodium Layered Oxides

Anionic oxygen redox represents a pivotal strategy to unlock high-energy-density sodium-ion batteries. However, this process is often hindered by irreversible oxygen oxidation and lattice oxygen release at high voltages, triggering structural degradation and capacity fade. Here we report a local electronic structure tuning strategy via zinc doping that stabilizes reversible oxygen redox. The high electronegativity of Zn induces a contraction of MnO6 octahedra, enabling the precise low-temperature (600 °C) synthesis of a P2/P3 solid-solution phase. This tailored cathode exhibits highly reversible anionic redox at 4.6 V, maintaining a single-phase reaction mechanism throughout cycling. Consequently, it delivers superior cycling stability with 86.8% capacity retention after 100 cycles at 5 C. P2/P3 phases facilitate reversible redox reactions and ensure structural integrity. This work establishes a paradigm for achieving stable anionic redox chemistry through local structural design, paving the way for cost-effective, high-energy-density sodium-ion batteries.