Fire-resistant, high-performance gel polymer electrolytes derived from poly(ionic liquid)/P(VDF-HFP) composite membranes for lithium ion batteries

High-performance gel polymer electrolytes (GPEs) with fire-resistant properties are highly desirable for lithium ion batteries (LIBs) with enhanced safety. Herein, we report a novel GPE derived from a porous poly(ionic liquid)/P(VDF-HFP) (PIL/P(VDF-HFP)) composite membrane prepared via a simple and scalable phase inversion method. The ion-dipole interactions between the PIL and P(VDF-HFP) endow the PIL/P(VDF-HFP) membrane with significantly enhanced mechanical performances and thermal stability. Flexible GPEs can be obtained after absorption of the liquid electrolytes into the PIL/P(VDF-HFP) membrane. The PIL/P(VDF-HFP) GPE exhibits a much higher ionic conductivity (1.78 × 10−3 S cm−1) compared to the liquid electrolytes absorbed in the commercial Celgard 2325 separator (3.5 × 10−4 S cm−1). The Li/LiFePO4 battery assembled with the GPE exhibits a high reversible capacity of 99.2 mAh g−1 at 12C and high discharge capacities of 138.4 and 125.4 mAh g−1 after 200 charge-discharge cycles at 1C and 4C, respectively. These performances are all superior to the Li/LiFePO4 battery using the commercial Celgard 2325 separator saturated with liquid electrolytes. Importantly, the PIL/P(VDF-HFP) GPE exhibits excellent fire-resistance, benefiting from the non-flammable property of the PIL. The as-developed GPE shows great potential for the practical application in LIBs with superior electrochemical performances and high safety.