Accelerated ion conduction by co-grafting of poly(ethylene glycol) and nitrile-terminated ionic liquid on poly(arylene ether sulfone) for solid electrolyte membranes for lithium ion battery

Abstract

Solid polymeric electrolytes (SPE) are fabricated from poly(arylene ether sulfone)-co-poly(ethylene glycol)/nitrile terminated ionic liquid (PAES-co-PEG/ILCN) for lithium ion battery. Ionic liquid (IL) based on 1-butyl-1-methylpyrrollidum bis(fluoromethanesulfonyl) imide (Pyr-TFSI) is prepared and blended with 0.5 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) for promotion of the lithium (Li) ion transport in the membrane. Because of the compatibility difference, the synthesized membranes show the phase separation between PAES and PEG/IL components where PAES plays a role as mechanically robust matrix and PEG/IL acts as ion transport pathways. The PAES-co-(PEG70/ILCN30) membrane containing 70 wt% of 0.5 M LiTFSI/Pyr-TFSI illustrates high Li ion conductivity (0.72 × 10−3 S cm−1) with the Li transport number value of 0.38 at room temperature. No thermal de-composition is observed up to 200 °C, maintaining the mechanical flexibility and rigidity with 1.25 MPa of tensile strength and 108% of elongation at fracture. The lithium ion phosphate (LiFePO4/SPE/Li) cell test exhibits the discharge capacity value of 139.7 mAh g−1 and high stable cyclic performance up to 100th cycle at 0.1 C-rate.