Lithium-rich,　manganese-based　layered　oxides　are　among　the　most　promising　cathode　materials　for　next-generation　lithium-ion　batteries　(LIBs),　offering　high　reversible　capacity,　elevated　operating　voltage,　and　cost-effectiveness　compared　to　conventional　cathodes.　However,　their　practical　application　is　hindered　by　irreversible　lattice　oxygen　loss　and　structural　degradation　during　cycling.　In　this　work,　Li-1.2[Mn0.54Ni0.13Co0.13]O-2　was　modified　via　in　situ　Mg2+　doping　and　uniform　Li2MnO3　surface　coating　to　address　these　challenges.　The　dual-modified　material　was　systematically　investigated　through　theoretical　analysis　and　validated　experimentally　using　structural,　morphological,　and　electrochemical　characterization　techniques.　Electrochemical　evaluations　revealed　that　the　synergistic　effect　of　Mg2+　doping　and　Li2MnO3　coating　significantly　improved　the　material＇s　performance,　delivering　a　high　discharge　capacity　of　193.9　mAh/g　at　1C　and　an　impressive　capacity　retention　of　86.4%　after　200　cycles.　Additionally,　the　52.73%　reduction　in　voltage　fade　achieved　through　Mg2+　doping　and　Li2MnO3　coating　further　confirms　the　enhanced　interfacial　stability　and　significantly　improved　long-term　cycling　durability　of　the　modified　electrode.