Plasticization of NaX-PEO solid polymer electrolytes by Pyr(13)X ionic liquids
Journal article, 2016
Addition of moderate contents (≤20 wt%) of ionic liquids (ILs) to binary solid polymer electrolytes (SPEs) is made to alter the overall SPE properties, foremost to increase the room temperature ionic conductivity. Sodium conducting ternary electrolytes, based on sodium salts; NaTFSI and NaFSI, the polymer poly(ethylene oxide) (PEO), and pyrrolidinium ILs; Pyr13TFSI and Pyr13FSI, with different compositions: NaX(PEO)n – Pyr13X (X = TFSI, FSI), have been prepared. Raman and dielectric spectroscopy as well as differential scanning calorimetry have been used to evaluate the plasticizing effect of the Pyr13 IL cation and the accompanying TFSI and FSI IL anions via changes in ionic association, crystallinity, polymer chain dynamics, and total ionic conductivity. While all the TFSI based systems seem rather insensitive to the addition of IL with respect to speciation, the situation is much less clear for the FSI based systems. Furthermore, the addition of ILs seems beneficial for inhibiting PEO crystallization, especially for the FSI anion, and also for enhancing the polymer chain dynamics, but yet the FSI based ternary electrolytes show lower ion conductivities as compared to the analogous TFSI based systems.
N-methyl-N-propylpyrrolidinium based ionic liquids