Tailoring Lattice Oxygen Redox and Robust Structure Stability in High‐Entropy Superlattice Layered Cathode for Superior Potassium‐Ion Storage

To address the inherent limitations of layered cathodes in terms of stability, kinetics, and energy density, a high-entropy superlattice layered oxide (K_0.7Mn_0.4Li_0.1Co_0.125Ni_0.125Fe_0.125Cu_0.125O₂, KMNCFCL_0.1) is proposed as a cathode for K-ion storage. High-entropy composition and [Li─O─K] configuration coupled with Cu─O covalency and local CuO₆ distortion trigger and stabilize lattice oxygen redox through the anionic-cationic redox inversion, essentially a premature ligand-to-metal charge transfer (LMCT), thereby alleviating potential issues of severe voltage hysteresis and capacity fade by restraining oxygen release and cation migration. Superior phase stability and strain tolerance with a solid-solution mechanism benefited from high-entropy stabilization, and "cocktail" effects can be successfully achieved by eliminating serious structural evolutions induced by Jahn-Teller (J-T) lattice distortion, O─O repulsion, and intercalation of electrolyte molecules. Furthermore, the enlarged interlayer spacing and disrupted K⁺/vacancy ordering facilitate rapid K-ion migration with a low diffusion barrier. Therefore, KMNCFCL_0.1 delivers a high energy density of 327.8 Wh kg^-1, superior cyclic stability with a long lifespan of over 300 cycles, and excellent rate capability. This research opens up new possibilities for achieving groundbreaking cathodic functionality in potassium layered oxides.