A Design Strategy for Durable Anionic Redox via Fluorine‐Induced Electronic Structure Modulation in In Situ Formed Disordered Phases

ABSTRACT Disordered cathode materials are attractive candidates for next‐generation lithium‐ion batteries (LIBs), but the intrinsic instability of anionic redox hinders their commercialization. Unlike conventional Li‐excess disordered systems limited by compositional constraints of Li 1+x M 1‐x O 2 , Immm ‐Li 2 NiO 2 offers a platform to access highly lithiated chemistries that enable in situ disorder formation during electrochemical cycling. This allows lattice O to contribute to charge compensation; however, O 2 release at high voltages compromises reversibility and cycling stability. To address this, fluorination generates a quadrupolar Li‐O‐M‐F configuration that lowers the Li─O─Li band energy level and delays the onset of anionic redox. This electronic structure modification suppresses O 2 evolution, enhances structural stability, and improves cycling performance. By coupling electrochemically induced disorder with stabilization through Li‐O‐M‐F units, this work establishes a new framework for engineering durable, high‐capacity cathodes, offering a blueprint for material design strategies that transcend stoichiometric restrictions and unlock stable anion redox functionality.