Speciation and Dynamics of Super-concentrated Electrolyte Solution for Next-generation Secondary Battery

Abstract

Ionic liquids are composed only of ionic species and have been attracted attention as electrolytes for fuel cells and next-generation secondary batteries. Ionic liquids are often found to have the specific ionic conduction mechanism. We recently found that the equimolar mixtures of N-methylimidazole (C1Im) and acetic acid (CH3COOH) have significant ionic conductivity, although only electrically neutral molecules practically exist in their equimolar mixture. We propose such liquids can be called as the pseudo-protic ionic liquids pPILs and consider that the specific proton conduction without static acid dissociation may occur in the mixture. On the other hand, solvate ionic liquids have been proposed as electrolyte solution for lithium sulfur battery. In this study, we discuss on ionic conduction mechanism for the nonequimolar pPILs. In addition, we demonstrate in-situ impedance measurements to reveal ion dynamics in electrode/electrolyte interface for the battery using the solvate ionic liquid.