Dynamic Chelate Effect on the Li+-Ion Conduction in Solvate Ionic Liquids

Lithium–glyme solvate ionic liquids (Li–G SILs), which typically consist of a lithium-ion (Li+) solvated by glymes of oligoethers and its counter anion, are expected as promising electrolytes for lithium secondary batteries. Additionally, a specific ligand-exchange Li+ conduction mechanism was proposed at the electrode/electrolyte interface of the cell using Li–G SILs. To reveal Li+ conduction in SILs, Li–G SILs with varying ethylene oxide chain lengths were investigated using various techniques that are sensitive to solution structure and dynamics. We found good correlations between the relaxation time of the slowest dielectric mode and the ionic conductivity as well as viscosity. We propose that a dynamic chelate effect, which is closely related to solvent exchange and/or contact ion-pair formation/dissociation, is important for Li+ conduction in these Li–G SILs.