Li/LiFePO₄ batteries with gel polymer electrolytes incorporating a guanidinium-based ionic liquid cycled at room temperature and 50 °c

Gel polymer electrolytes composed of PVdF-HFP microporous membrane incorporating a guanidinium-based ionic liquid with 0.8 mol kg^-1 lithium bis(trifluoromethanesulfonylimide) are characterized as the electrolytes in Li/LiFePO₄ batteries. The ionic conductivity of these gel polymer electrolytes is 3.16 × 10^-4 and 8.32 × 10^-4 S cm^-1 at 25 and 50 °C, respectively. The electrolytes show good interfacial stability towards lithium metal and high oxidation stability, and the decomposition potential reaches 5.3 and 4.6 V (vs. Li/Li⁺) at 25 and 50 °C, respectively. Li/LiFePO₄ cells using the PVdF-HFP/1g13TFSI-LiTFSI electrolytes show good discharge capacity and cycle stability, and no significant loss in discharge capacity of the battery is observed over 100 cycles. The cells deliver the capacity of 142 and 150 mAh g^-1 at the 100th cycling at 25 and 50 °C, respectively.