Co-free　Li-rich　Li1.2Ni0.2Mn0.6O2　(LR)　cathode　shows　the　highest　working　capacity　that　can　be　applied　to　high-energy　density　Li-ion　batteries　(LIBs).　However,　poor　cycle　stability　and　voltage　decay　caused　by　phase　transition　are　always　hindering　its　further　development.　Herein,　a　novel　medium-entropy　Li-rich　Mn-based　cathode　material　(LRMEF)　was　synthesized　via　a　simple　sol-gel　method.　The　introduction　of　multivalent　ions　(Al3+/Cu2+　doping　at　Mn　sites　and　F−　doping　at　O　sites)　effectively　mitigates　the　Jahn-Teller　distortion　of　Mn　ions　and　suppresses　oxygen　release.　High-angle　annular　dark-field　scanning　transmission　electron　microscopy　(HAADF-STEM)　images　confirm　that　this　synergistic　doping　strategy　induces　the　in-situ　formation　of　an　approximately　3　nm-thick　spinel　surface　layer,　which　significantly　enhances　structural　stability　and　ion　diffusion　kinetics.　Besides,　a　series　of　in-situ/ex-situ　characterization　methods　and　density　functional　theory　(DFT)　calculations　have　been　carried　out　to　fundamentally　shed　light　on　the　optimized　structure-activity　relationship　and　reaction　mechanism.　As　a　result,　the　LR　material　with　entropy　regulation　and　anion　doping　exhibits　excellent　cycling　stability　(189.2　mAh　g−1　at　1　C　with　84　%　capacity　retention　after　300　cycles),　rate　performance　(164.1　mAh　g−1　at　5　C),　and　voltage　retention　(82.7　%　at　1　C　after　300　cycles),　demonstrating　great　application　prospects　in　future　high-energy-density　LIBs.　©　2025　Science　Press