Effect Of Ionic Liquid On Semi–crystalline Poly(vinylidene fluoride–co–hexafluoropropylene) Solid Copolymer Electrolytes

Solid copolymer electrolytes based on poly(vinylidene fluoride–co–hexafluoropropylene) (PVdF– HFP) as the host polymer, containing lithium perchlorate salt (LiClO4) and 1–butyl–3– methylimidazolium chloride ionic liquid (BmImCl) had been prepared through solution casting method. The highest ionic conductivity of (1.49±0.02)×10 -3 Scm -1 was achieved by doping 80 wt% of BmImCl at room temperature. These copolymer electrolytes followed Arrhenius rules as proven in temperature–dependence ionic conductivity study. X–ray diffraction (XRD) revealed lower crystalline portion of the polymer electrolytes. This has been further proven in differential scanning calorimetry (DSC) by determining the degree of crystallinity of copolymer electrolytes. Upon addition of 40 wt% of BmImCl, the glass transition, melting and crystallization temperatures are significantly reduced as visualized in DSC thermograms. However, both of melting and crystallization peaks are absent by adding more 40 wt% of BmImCl. Thermogravimetric analysis (TGA) demonstrated that the thermal stability of solid copolymer electrolytes was reduced upon addition of BmImCl. However, the stability of this ionic liquid–based solid copolymer electrolyte was up to 232 °C as proven in TGA curve.