Synthesis and ionic conductivity of a novel ionic liquid polymer electrolyte

Hyperbranched poly(glycidol) (HPG) containing hydroxyl groups is firstly synthesized via anionic polymerization, and then reacts with thionyl chloride to form chlorine end-terminated hyperbranched poly(glycidol) (HPG-Cl). Different ionic liquid polymers are synthesized from the reaction of HPG-Cl with N-methylimidazole and then anion exchange with hexafluorophosphoric acid and sodium tetrafluoroborate. The structure and properties of the obtained ionic liquid polymers are characterized by 1 H NMR, ATR-FTIR, DSC and TGA, respectively. Ionic conductivity of the polymer electrolytes composed of ionic liquid polymer and lithium bis(trifluoromethanesulfonimide) (LITFSI) is investigated by electrochemical impedance spectroscopy. The results show that the ionic conductivity of the prepared ionic liquid polymer electrolyte can reach 3.5 × 10 −4 Scm −1 at 30 °C when the weight ratio of ionic liquid polymer ([HPG-MeIm]BF 4 ) to lithium salt (LiTFSI) is 4.5.