Lithium ion transport and solvation in N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide-propylene carbonate mixtures

Kühnel R-S, Balducci A

Abstract

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 14TFSI)-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 PYR14TFSI-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. © 2014 American Chemical Society.