Abstract: Flammable polymer electrolytes are prone to fire after the abuse of short circuits，mechanical shock，and thermal runaway. Therefore，flame-retardant modification for lithiumion batteries polymer electrolytes exhibits particularly necessary. This paper reviews the research progress of flame-retardant polymer electrolytes. First，the two flame-retardant mechanisms of gas-phase and condensed phase during the combustion of polymer electrolytes，as well as various evaluation indicators for flame-retardant performance，are introduced. Then it summarizes the advantages and disadvantages of different flame-retardant compounds， and the flame retardants of polymer electrolytes have been classified for discussion according to the differences in flame-retardant elements. Finally，the application prospects for polyphosphonate and phosphazene compounds in the field of flame-retardant polymer electrolytes are predicted，and the future research directions of flame-retardant polymer electrolytes are prospected.

Key words: lithium-ion battery, safety, polymer electrolytes, flame-retardant