Fig. 2. Structure-property relationships between fluorination degree and ionic conductivity.

a Comparison of chemical structures and electrostatic potentials (ESP) of various ether solvents including DEE, BTFE, BDE, TFFE, DFE, and BFE. b–d ¹⁹F NMR of BFE, DFE, and TFFE before and after the salt dissolution (Reference: CF₃COOH). Green sphere represents Li⁺ ion, while sticks in white, pink, light blue and red color represent H, F, C, and O atoms, respectively. e ⁷Li NMR of LiFSI salts in different electrolytes. f Solvating energies of DEE, TFFE, DFE, and BFE electrolytes. g Bulk ionic conductivities of various electrolytes at 30 °C, including DEE, BTFE, BDE, TFFE, DFE, and BFE. h Bulk ionic conductivity of BFE and previously reported fluorinated electrolytes at 30 °C. Because LiFSI is almost insoluble in BTFE and BDE, the bulk ionic conductivity value is not reported in the chart.