Polymer Electrolytes for LIBs Based on Perfluorinated Sulfocationic Nepem-117 Membrane and Aprotic Solvents

Polymer electrolytes have been obtained based on Nepem-117 membranes in Li+ form with intercalated polar aprotic solvents, such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMA), and solvent mixtures, such as ethylene carbonate-propylene carbonate (EC-PC), EC-DMA, EC-PC-DMA, EC-PC-DMA-tetrahydrofuran (THF). The obtained electrolytes have been characterized by IR-, impedance and 7Li pulsed field gradient NMR spectroscopy. Ion mobility increases with higher degree of solvation of the membranes. A method is demonstrated to determine the solvent uptake corresponding to the percolation threshold. With comparable solvent uptake, materials containing a solvent with a higher permittivity and a lower viscosity have higher values of ionic conductivity. The membranes containing the three-component mixture of EC-PC-DMA show the highest ionic conductivity values (8.1 and 2.1 mS/cm at +25 and -20 °С). Such values exceed the conductivity of electrolytes based on the Nafion membranes solvated with aprotic solvents.