Preparation and characterization of solid polymer electrolytes based on PHEMO and PVDF-HFP

Polymer electrolyte membranes consisting of a novel hyperbranched polyether PHEMO (poly(3-{2-[2-(2-hydroxyethoxy) ethoxy] ethoxy}methyl-3′-methyloxetane)), PVDF-HFP (poly(vinylidene fluoride-hexafluoropropylene)) and LiTFSI have been prepared by solution casting technique. X-ray diffraction of the PHEMO/PVDF-HFP polymer matrix and pure PVDF-HFP revealed the difference in crystallinity between them. The effect of different amounts of PVDF-HFP and lithium salts on the conductivity of the polymer electrolytes was studied. The ionic conductivity of the prepared polymer electrolytes can reach 1.64 × 10^{- 4} S·cm^{- 1} at 30 °C and 1.75 × 10^{- 3} S·cm^{- 1} at 80 °C. Thermogravimetric analysis informed that the PHEMO/PVDF-HFP matrix exhibited good thermal stability with a decomposition temperature higher than 400 °C. The electrochemical experiments showed that the electrochemical window of the polymer electrolyte was around 4.2 V vs. Li⁺/Li. The PHEMO/PVDF-HFP polymer electrolyte, which has good electrochemical stability and thermal stability, could be a promising solid polymer electrolyte for polymer lithium ion batteries.