Non-flammable Gel Polymer Electrolyte for Enhancing the Safety and High-Temperature Performance of Lithium-Ion Batteries

As the applications of lithium-ion batteries (LIBs) have expanded, battery safety has emerged as a major concern because of the thermal runaway of LIBs arising from the use of flammable liquid electrolytes (LEs). Gel polymer electrolytes (GPEs) have been considered as potential candidates to replace LEs and improve the thermal safety of LIBs. In our study, a chemically cross-linked nonflammable GPE was synthesized and used in an LIB. A cross-linking agent, spirocyclic pentaerythritol diphosphate perfluorinated ether acrylate, comprising a phosphorus moiety and a fluoroether chain, was designed and synthesized to prepare a nonflammable cross-linked GPE. The obtained GPE effectively suppressed the deleterious reactions of the LE and imparted nonflammable characteristics. The pouch-type graphite/LiNi0.6Co0.2Mn0.2O2 cell with a nonflammable GPE delivered an initial discharge capacity of 146.7 mAh g–1 with a capacity retention of 71.1% after 300 cycles at 0.5 C and 55 °C. Moreover, the chemically cross-linked GPE exhibited excellent dimensional and thermal stability, which allowed for the safer operation of LIBs even under harsh conditions. This work provides guidelines for designing nonflammable electrolyte systems for advanced LIBs with high safety, enhanced thermal stability, and good cycling characteristics at elevated temperatures.