Influence of lithium salt addition on ionic conductivity and transporting properties of lithium bis(trifluoromethanesulfonyl)imide-doped glycine-based ionic liquid electrolyte

摘要

The effects of the incorporation of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) on the ionic transporting and physicochemical properties of a glycine-based ionic liquid (IL) are studied. The ionization conditions of each ionic species in LiTFSI-doped glycine-based ionic liquid electrolytes ([MGlyA][TFSI]), are characterized by diffusion coefficients of the species measured using the pulsed gradient spin-echo (PGSE) NMR technique. Temperature-dependent viscosity, ionic conductivity, molar conductivity, and self diffusion coefficient in neat [MGlyA][TFSI] and LiTFSI-doped [MGlyA][TFSI] followed the Vogel-Tamman-Fulcher equation at all concentrations. The experimental molar conductivity (Λ) of neat [MGlyA][TFSI] and LiTFSI-doped [MGlyA][TFSI] is lower than that of the calculated molar conductivity (Λ_(NMR)) from PGSE NMR technique over the entire temperature range, demonstrating that not all the diffusive species contribute to the ionic conduction, that is, free-ions, ionic pairs, and/or clusters coexist in ILs.