Influence of 1-Ethyl-3-methylimidazolium Bis(Fluorosulfonyl) Imide on the Conductivity, Thermal Properties and Molecular Structure of Poly (Vinylidene Fluoride-hexafluoropropylene) (PVDF-HFP) Polymer Electrolyte

Ionic liquids are used in sodium batteries instead of organic solvents because the high flammability of organic solvents can cause serious safety issues, such as fires or explosions.In this study, ionic liquid polymer electrolyte (ILPE) films were prepared using a casting technique by adding 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide [C2C1im][FSI] ionic liquid in different ratios (10 wt.%, 20 wt.%, 30 wt.%, 40 wt.% and 50 wt.%)into the poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) solution as a host polymer.The shift in wavenumbers of the vibrational modes of S-N-S and SO2 indicated the interactions between PVDF-HFP and [C2C1im][FSI] ionic liquid.The intensity of the crystalline X-ray diffraction (XRD) peaks decreased consistently with the addition of higher amounts of [C2C1im][FSI], suggesting that the presence of ionic liquid reduced the crystallinity of PVDF-HFP.The conductivity of ILPEs generally increased with increasing amounts of ionic liquid, and the highest conductivity at room temperature of 8.04 10 -5 S cm -1 was recorded for the sample loaded with 50 wt.%[C2C1im] [FSI].Thermal gravimetric analysis (TGA) indicated that all ILPE samples could withstand temperatures of up to 300 C, as no significant weight loss was observed.Differential scanning calorimetry (DSC) analysis indicated that the melting temperature (Tm) decreased with increasing amounts of ionic liquid.These findings imply that the ILPE containing 50 wt.%[C2C1im][FSI] may be taken into consideration for battery applications.