Solid-state　polymer　electrolytes　(SPEs)　present　poor　anti-oxidation　ability,　low　ionic　conductivity　and　high　flammability,　which　greatly　restrict　their　applications　in　high-voltage　solid-state　lithium　metal　batteries.　Herein,　we　uniformly　graft　the　lithium　phenyl　phosphate　(LPPO)　on　polyvinylidene　difluoride　(PVDF)　by　dehydrofluorination　and　Friedel-Crafts　alkylation　reactions　to　create　a　multifunctional　PVDF-LPPO　SPE　with　branched　topology.　The　LPPO　serves　as　a　single　ion　conductor,　flame　retardant　and　cathode　electrolyte　interface　formation　agent　not　only　greatly　improves　the　ionic　conductivity,　fireproof　property　and　electrochemical　stability　of　SPE,　but　also　remarkably　suppresses　the　side　reactions　with　both　cathode　and　lithium　metal　anode.　An　additional　and　uniform　Li-ion　transmission　path　is　constructed　by　LPPO　to　remarkably　reduce　the　activation　energy　and　enhance　the　lithium-ion　transference　number　of　PVDF-LPPO　SPE.　The　solid-state　LiNi0.8Co0.1Mn0.1O2||PVDF-LPPO||Li　batteries　stably　cycle　for　1550　times　between　2.8　and　4.3　V　at　1　C　and　1000　times　under　a　high　charging　voltage　of　4.5　V.　The　transformation　of　layered　structure　to　rock-salt　phase　of　NCM811　particles　is　greatly　suppressed　during　long　cycling　by　a　stable　and　uniform　LPPO　derived　cathode　electrolyte　interface.　This　work　provides　a　precise　operation　method　for　modifying　structure　of　polymer　electrolyte　to　achieve　outstanding　special　properties　of　lithium　metal　solid-state　batteries.　©　2022