Stable　electrolytes　are　urgently　required　for　lithium-ion　batteries　based　on　lithium-rich　layered　oxides　(LLOs),　which　generally　suffer　from　fast　capacity　and　voltage　decay　at　high　voltages　up　to　4.8　V.　Herein,　we　report　a　salt-concentrated　electrolyte　consisting　of　4　M　lithium　hexafluorophosphate　(LiPF6)　salt　in　ester　solvents　of　fluoroethylene　carbonate　(FEC)　and　dimethyl　carbonate　(DMC)　to　alleviate　the　above　challenges.　The　solvent　structure　in　the　4　M　electrolyte　shows　more　volatile　DMC　integrated　with　Li+　and　more　free　antioxidative　FEC　compared　with　a　1　M　electrolyte,　broadening　the　operation　voltage.　Simultaneously,　this　electrolyte　endows　a　thin　yet　high　elasticity　modulus　LiF-rich　interphase　on　the　LLOs　surface,　which　can　effectively　prevent　diverse　side　reactions　and　transition　metal　migration,　consequently　improving　the　electrochemical　performance　with　a　voltage　decay　of　only　0.46　mV/cycle　and　capacity　retention　of　80.3%　after　500　cycles.　This　simple　and　effective　approach　boosts　the　development　of　high-energy-density　batteries　using　LLOs.