In Situ Fabricated Non-Flammable Gel Polymer Electrolyte with Stable Interfacial Compatibility for Safer Lithium-ion Batteries

Gel polymer electrolytes are viewed as one of the highly ideal substitutes for commercial liquid electrolytes due to their excellent properties of non-flowing, non-volatile, high burning point, and compatibility with industrial systems, which collectively contribute to enhanced safety characteristics of batteries. However, the interfacial compatibility issues arising from the unreacted monomers pose significant challenges, leading to poor interfacial compatibility, parasitic reactions, and a subsequent deterioration in battery safety. Herein, a non-flammable gel polymer electrolyte has been designed by in situ polymerization of Poly (ethylene glycol) diacrylate (PEDGA) with the interfacial reinforcement of Ethoxy (pentafluoro) cyclotriphosphazene (PFPN), to improve the interfacial compatibility and further enhance the safety properties. The gel polymer electrolyte not only forms a stable interface uniformly to resist against the unreactive monomers but also delays the contact reactions and mitigates the chemical crosstalk. The thermal performances with various electrolytes are evaluated comprehensively, and the mechanism for high safety has also been revealed. The incubation time of thermal runaway has been effectively put off from 10.78 to 36.34 h, and the maximum temperature rise (dT/dt) _max been reduced in half from 612.0 to 388.2 °C s⁻¹. This work provides an effective strategy for designing efficient polymer electrolytes for high-safety batteries.