Styrenic BAB triblock copolymers functionalized with lithium (N-tetrafluorophenyl)trifluoromethanesulfonamide as solid single-ion conducting electrolytes

Solid single-ion conducting electrolytes based on well-defined block copolymers show great potential for use in lithium batteries. Here, we report on triblock copolymers with an ion conductive poly(ethylene oxide) (PEO) center block and two flanking blocks of poly(lithium 2,3,5,6–tetrafluorostyrene-4-trifluoromethanesulfonamide). The copolymers were prepared through atom transfer radical polymerization (ATRP) of pentafluorostyrene using a bidirectional PEO macroinitiator, followed by quantitative nucleophilic aromatic substitution of the p-fluorine atoms with sodium trifluoromethanesulfonamide. The ionic content of the copolymers was readily regulated by controlling the monomer feed ratio in the ATRP to obtain [EO]/[Li] between 4 and 88, and thermal decomposition occurred only above ~300 °C to indicate a high thermal stability. Above the melting point of the PEO center block, a copolymer containing 16 wt% of the flanking blocks ([EO]/[Li] = 40) reached a conductivity of 5.7·10^-6 S cm^-1 at 70 °C. The overall results indicate that well-designed polymers functionalized with lithium (N-perfluorophenyl)trifluoromethanesulfonamide groups show promise as solid single-ion conducting electrolytes.