Electrochemical Characterization of Poly(vinylidene Fluoride-Co-hexafluoro Propylene) Based Electrospun Gel Polymer Electrolytes Incorporating Room Temperature Ionic Liquids As Green Electrolytes for Lithium Batteries

A series of gel polymer electrolytes (GPEs) based on electrospun membranes of poly(vinylidene fluoride-co-hexafluoropropylene) [P(VdF-co-HFP)] incorporating room temperature ionic liquids (RTILs), 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide complexed with lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) as electrolytes have been prepared and their fundamental electrochemical properties were investigated. The morphology of electrospun membranes was examined by a field emission scanning electron microscope (FE-SEM). The membranes show uniform morphology with an average fiber diameter of 780nm, high porosity and high electrolyte uptake. GPEs were prepared by soaking the electrospun membranes in 1M LiTFSI in RTILs for 1h and exhibit a high ionic conductivity of 2.4×10−3–4.5×10−3Scm−1 at 25°C. A Li/GPEs/LiFePO4 cell using these RTILs delivers high discharge capacity (~140mAh g−1) when evaluated at 25°C at 0.1C-rate and exhibits a very stable discharge capacity under continuous cycling. Among the GPEs, EMITFSI shows the highest electrochemical properties although the solid electrolyte interface (SEI) layer was not formed.