Lithium Ion Transport and Solvation in N-Butyl-N-methylpyrrolidinium Bis(trifluoromethanesulfonyl)imide–Propylene Carbonate Mixtures

Ionic liquid–solvent mixtures are electrolytes for electrochemical energy storage devices that can combine low flammability with high conductivity. Here, we report about (lithium) transport properties of and Li + solvation in N -butyl- N -methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 14 TFSI)–propylene carbonate mixtures containing LiTFSI. Transport properties are investigated by viscosity, conductivity, and diffusion measurements. Interestingly, Li + ion diffusion is enhanced the most upon PC addition to PYR 14 TFSI–LiTFSI. Raman measurements show a decreasing contribution of TFSI – to the coordination of Li + upon PC addition to the electrolyte while the total degree of ion dissociation goes through a minimum.