Gel polymer electrolyte based on PVDF-HFP matrix composited with rGO-PEG-NH2 for high-performance lithium ion battery

A series of composite gel polymer electrolytes (GPEs) based on poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), 1-ethtyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), lithium bis(trifluoromethane) sulfonimide (LiTFSI) and covalent linked 2,2''-(ethylenedioxy) bis (ethylamine) to reduced graphene oxide (rGO-PEG-NH2) have been successfully prepared by solution casting method. With the increase of [EMIM][TFSI] and rGO-PEG-NH2 content, the crystallinity of the GPE decreased, and the thermal decomposition temperature increased significantly. A high-speed lithium ion transport network was formed in the 3P5E2LG-10 GPE, with rGO as the connection site and PEG as the bridge. 3P5E2LG-10 GPE exhibited a conductivity of 2.1 × 10−3 S cm−1 at 30 °C, a lithium ion transference number of 0.45, and a electrochemical window of 5.0 V. The 3P5E2LG-10 based cell exhibited more than 99% columbic efficiency and the initial discharge capacity reached the maximum of 163.7 mAh/g, and capacity retention was about 88% after 80 cycles at 0.1C. 3P5E2LG-10 GPE will have great potential for lithium ion battery with high safety and long cycle life.