Effects of water on the structure and transport properties of room temperature ionic liquids and concentrated electrolyte solutions*

Abstract

Transport properties and the associated structural heterogeneity of room temperature aqueous ionic liquids and especially of super-concentrated electrolyte aqueous solutions have received increasing attention, due to their potential application in ionic battery. This paper briefly reviews the results reported mainly since 2010 about the liquid–liquid separation, aggregation of polar and apolar domains in neat RTILs, and solvent clusters and 3D networks chiefly constructed by anions in super-concentrated electrolyte solutions. At the same time, the dominating effect of desolvation process of metal ions at electrode/electrolyte interface upon the transport of metal ions is stressed. This paper also presents the current understanding of how water affects the anion–cation interaction, structural heterogeneities, the structure of primary coordination sheath of metal ions and consequently their transport properties in free water-poor electrolytes.

History repeats itself again: Will the mistakes of the past for ILs be repeated for DESs? From being considered ionic liquids to becoming their alternative: the unbalanced turn of deep eutectic solvents

“…103 Consequently, understanding the effects of different amounts of water on the liquid structure of ILs and DESs/ESs at the molecular level is highly important, since it allows control of their macroscopic properties. Although the effect of water on ILs' structure is well understood and a substantial amount of work has been published, 104 the same cannot be said for DESs/ESs, which have been studied to a considerably lesser extent and with a greater emphasis on mixtures of ChCl with U. 105,106 Chunyan published a comprehensive review 107 of similarities and differences of water in ILs/ionic DESs and ILs/ionic DESs in water.…”