Recent Progress in Flame-Retardant Polymer Electrolytes for Solid-State Lithium Metal Batteries

Lithium-ion batteries (LIBs) have been widely applied in our daily life due to their high energy density, long cycle life, and lack of memory effect. However, the current commercialized LIBs still face the threat of flammable electrolytes and lithium dendrites. Solid-state electrolytes emerge as an answer to suppress the growth of lithium dendrites and avoid the problem of electrolyte leakage. Among them, polymer electrolytes with excellent flexibility, light weight, easy processing, and good interfacial compatibility with electrodes are the most promising for practical applications. Nevertheless, most of the polymer electrolytes are flammable. It is urgent to develop flame-retardant solid polymer electrolytes. This review introduces the latest advances in emerging flame-retardant solid polymer electrolytes, including Polyethylene oxide (PEO), polyacrylonitrile (PAN), Poly (ethylene glycol) diacrylate (PEGDA), polyvinylidene fluoride (PVDF), and so on. The electrochemical properties, flame retardancy, and flame-retardant mechanisms of these polymer electrolytes with different flame retardants are systematically discussed. Finally, the future development of flame-retardant solid polymer electrolytes is pointed out. It is anticipated that this review will guide the development of flame-retardant polymer electrolytes for solid-state LIBs.