Weakly Coordinating Fluorine-Free Polysalt for Single Lithium-Ion Conductive Solid Polymer Electrolytes

Abstract

A novel single lithium-ion conducting (SLIC) polymer electrolyte containing a weakly coordinating fluorine-free polysalt is presented. The polysalt, lithium poly(4-styrenesulfonyl)(dicyano)methide (LiPSDM), is conceived on the basis of a fluorine-free green chemistry, and motivated by the highly performing non-fluorinated lithium tricyanomethanide (LiTCM) salt. The electrolyte comprising LiPSDM and poly(ethylene oxide) (PEO) shows good thermal stability, decent ionic conductivity, and high lithium transference number. In stark contrast to other fluorine-free polysalts, such as, poly(4-styrenesulfonate) (LiPSS), the replacement of −SO3− moiety by −SO2C(−)(CN)2 improves the flexibility of the anion and the charge delocalization, leading to an improved amorphization of PEO and an overall better performance. Moreover, solid-state nuclear magnetic resonance (NMR) measurements are performed to unravel the role of anion chemistry on the fundamental transport properties of SLICs. The present work is believed to facilitate the design of high-performance fluorine-free polymer electrolytes which are important building blocks for safe, green, and sustainable battery technologies.