Solid polymer electrolytes from lithium (perfluorovinylether) sulfonate—Derived salts dissolved in high-molecular-weight poly(ethylene oxide)

This paper describes synthesis of lithium salts of partially fluorinated aliphatic ether sulfonates, which are prepared by coupling of fluorinated vinyl ether sulfonated to partially fluorinated alcohols or diols. The resulting salts exhibit high ionic conductivity. Trends in conductivity with structure indicate that a lot of fluoroalkyl character in the salts favors high conductivity, which probably reflects delocalization of negative charge from sulfonates. [Display omitted] •Lithium sulfonate units were attached to partially fluorinated alcohols.•Solid polymer electrolytes (SPEs) were prepared in a polyethylene oxide host.•SPE ionic conductivities obey the Vogel-Tammann-Fulcher (VTF) relation.•SPE ionic conductivities vary with anion degree of fluorination. Solid polymer electrolytes (SPEs) were prepared using new lithium salts derived from a lithium (perfluorovinylether)sulfonate (CF2CFOCF2CF2SO3Li) coupled to either a partially fluorinated alcohol (monolithium series) or a partially fluorinated diol (dilithium series). High-molecular-weight poly(ethylene oxide) (PEO) was used as the polymeric host. SPE characterization was accomplished using modulated differential scanning calorimetry (MDSC), 1H and 19F NMR spectroscopy and electrochemical impedance spectroscopy (EIS). Ionic conductivities for SPEs made using the new salts, and also using lithium triflate (LiTf) and lithium bis[(trifluoromethyl)sulfonyl]imide (LiTFSI) as controls, were measured over a temperature range between 120°C and room temperature for materials with an ethylene oxide to lithium (EO/Li) ratio of 30–1. Conductivities varied depending upon the structure of the alcohol or diol used to make the salt, and were generally higher for alcohols/diols having more perfluorinated methylene groups.