Modulating Local Oxygen Coordination to Achieve Highly Reversible Anionic Redox and Negligible Voltage Decay in O2‐Type Layered Cathodes for Li‐Ion Batteries

O2‐type layered oxides have emerged as promising cathode materials for high‐energy lithium‐ion batteries, offering a solution to mitigate voltage decay through reversible transition metal (TM) migration between TM and Li layers during cycling. However, achieving a fully reversible oxygen redox remains a significant challenge. Here, this is addressed by introducing Li─O─Li configurations in the layered structure of Li0.85□0.15[Li0.08□0.04Ni0.22Mn0.66]O2 (O2‐LLNMO), where □ represents vacancies. This adjustment alters the redox‐active oxygen environment and increases the energy gap between the O 2p nonbonding and TM─O antibonding bands. As a result, the contribution of lattice oxygen to capacity is significantly enhanced, improving the reversibility of oxygen redox processes. The O2‐LLNMO cathode demonstrates minimal voltage decay (0.13 mV per cycle) and excellent cycling stability, retaining 95.8% of its capacity after 100 cycles. A novel strategy is presented to design high‐performance layered oxides with stable anionic redox activity, advancing the development of next‐generation lithium‐ion batteries.