Ion conductivity and physicochemical properties of lithium and sodium forms of perfluorinated sulfocationic membranes swollen with ethylene and propylene carbonates

The development of efficient polymer electrolytes represents a crucial step in enhancing the safety of lithium and sodium-ion batteries. The perfluorinated membranes studied in this work offer a cost-effective alternative to the commonly used Nafion membrane. The paper presents data on a study of the molecular and supramolecular structure, thermal stability, degree of saturation, and ionic conductivity of polymer electrolytes based on the lithium and sodium forms of membranes swollen with ethylene and propylene carbonates. The molecular structure and thermal stability of the studied membranes are identical to those of the Nafion. In terms of ionic conductivity, these membranes are on par with, and in some cases outperform, Nafion. The conductivity of the lithium form of the studied membranes, plasticized with propylene carbonate, demonstrates a slight decrease in conductivity from 9 × 10⁻⁴ to 2 × 10⁻⁵ S cm^–1 with temperature change from + 70 to − 60 °C. Outstanding low-temperature performance along with flexibility and elasticity makes them an extremely promising option for use as electrolytes in Li-ion batteries.