Characterization and application of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide ionic liquid–based gel polymer electrolyte prepared in situ by photopolymerization method in lithium ion batteries

Ionic liquid gel polymer electrolyte (IL-GPE) was prepared in situ by photocuring of a mixture containing N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (IL), lithium bis(trifluoromethane-sulphonyl)imide and ethoxylated bisphenol A diacrylate. The obtained IL-GPE was characterized by differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), cyclic and linear sweep voltammetry (CV and LSV) and galvanostatic charging/discharging. Ionic conductivity of the IL-GPE reached 0.64·10−4 S cm−1 at 25 °C and increased with a rise in temperature to 4.8 10−3 S cm−1 at 95 °C. Electrochemical stability of the IL-GPE is ca. 4.8 V vs. Li/Li+. The assembled cell consisting of the Li/IL-GPE/LiFePO4 exhibited stable cycle properties and high capacity above 162 mAh g−1 after 50 cycles (96% of theoretical capacity, which for LiFePO4 is 170 mAh g−1) at the C/20 rate and 25 °C. The results obtained indicate that the new IL-GPE is a promising candidate as an electrolyte for flexible lithium ion batteries.