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 Li_0.85□0.15[Li_0.08□0.04Ni_0.22Mn_0.66]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.