Li-rich　Mn-based　cathode　materials　(LRMs)　with　high　specific　capacity　are　considered　as　one　of　the　most　promising　cathodes　in　the　next-generation　lithium-ion　batteries.　However,　the　mismatch　between　high-voltage　LRM　cathodes　and　conventional　carbonate　electrolytes　causes　a　series　of　problems　such　as　cathode　structure　degradation,　transition　metal　dissolution,　and　continuous　electrolyte　decomposition.　Herein,　we　demonstrate　a　nonflammable　and　highly　oxidation-resistant　electrolyte　by　introducing　methyl　(2,2,2-trifluoroethyl)　carbonate　(FEMC)　as　the　single　solvent.　Theoretical　calculations　show　that　the　low　binding　energy　between　FEMC　and　Li+　promotes　the　desolvation　process　of　Li+　while　reducing　the　competition　with　anions,　which　is　beneficial　for　more　anions　to　enter　the　first　solvation　shell　structure　of　Li+.　This　regulation　in　solvation　structure　optimizes　the　cathode-electrolyte　interphase　(CEI)　components　and　forms　a　durable　and　inorganic-rich　CEI　layer　on　the　cathode　interface.　Meanwhile,　the　low　viscosity　and　flame-retardant　properties　of　the　FEMC　molecule　also　improve　the　wettability　and　safety　of　the　electrolyte.　Therefore,　the　assembled　Li‖LRM　batteries　with　the　single-solvent　electrolyte　exhibit　a　high　capacity　retention　of　83.9%　after　400　cycles　in　the　voltage　range　of　2-4.8　V　at　1C.　Even　at　the　high　cut-off　voltage　of　5　V,　a　high　capacity　retention　of　91.9%　is　achieved　after　150　cycles.　This　work　provides　new　insights　into　the　development　of　high-safety　and　high-voltage　electrolytes　for　high-energy-density　lithium-ion　batteries.　©　2025　The　Royal　Society　of　Chemistry.