The　poor　ambient　ionic　transport　properties　of　poly(ethylene　oxide)　(PEO)-based　SPEs　can　be　greatly　improved　through　filler　introduction.　Metal　fluorides　are　effective　in　promoting　the　dissociation　of　lithium　salts　via　the　establishment　of　the　Li-F　bond.　However,　too　strong　Li-F　interaction　would　impair　the　fast　migration　of　lithium　ions.　Herein,　magnesium　aluminum　fluoride　(MAF)　fillers　are　developed.　Experimental　and　simulation　results　reveal　that　the　Li-F　bond　strength　could　be　readily　altered　by　changing　fluorine　vacancy　(VF)　concentration　in　the　MAF,　and　lithium　salt　anions　can　also　be　well　immobilized,　which　realizes　a　balance　between　the　dissociation　degree　of　lithium　salts　and　fast　transport　of　lithium　ions.　Consequently,　the　Li　symmetric　cells　cycle　stably　for　more　than　1400　h　at　0.1　mA　cm-2　with　a　LiF/Li3N-rich　solid　electrolyte　interphase　(SEI).　The　SPE　exhibits　a　high　ionic　conductivity　(0.5　mS　cm-1)　and　large　lithium-ion　transference　number　(0.4),　as　well　as　high　mechanical　strength　owing　to　the　hydrogen　bonding　between　MAF　and　PEO.　The　corresponding　Li//LiFePO4　cells　deliver　a　high　discharge　capacity　of　160.1　mAh　g-1　at　1　C　and　excellent　cycling　stability　with　100.2　mAh　g-1　retaining　after　1000　cycles.　The　as-assembled　pouch　cells　show　excellent　electrochemical　stability　even　at　rigorous　conditions,　demonstrating　high　safety　and　practicability.　©　2024　American　Chemical　Society.