Phosphorus‐Fixed Stable Interfacial Nonflammable Gel Polymer Electrolyte for Safe Flexible Lithium‐Ion Batteries

Abstract A high content of flame retardant in non‐combustible electrolytes leads to deterioration of the electrochemical performance of lithium‐ion batteries (LIBs). Besides, fire hazard of most non‐flammable electrolytes is studied in coin cell, for which it is impossible to reveal real performance. Thus, the stable interfacial, phosphorus‐fixed nonflammable gel polymer electrolyte (GPE) with low content of flame retardant (7.5 wt.%) has been designed by in situ polymerization of tri(acryloyloxyethyl) phosphate and triethylene glycol dimethacrylate in electrolyte. After being heated by fire for >10 s, the GPE is still not ignited. The average capacity attenuation rate of graphite//GPE//Li (0.008%) is much lower than that of the liquid electrolyte (0.039%). Besides, the nonflammable GPE based pouch cell with good flexibility and excellent fire safety is prepared. No fire, no thermal runaway and no electrolyte leakage occur for 1 Ah flexible pouch cell with 100% SOC. The mechanism for high safety of pouch cell has also been revealed. First the amount of combustible pyrolysis products from thermal degradation of GPE is reduced through forming P and F containing char. Second, the combustion of GPE is extinguished through OH free radical quenching effect of flame retardant molecular. This work provides a guideline for designing high‐safety LIBs.