Conductivity, Viscosity, and Their Correlation of a Super-Concentrated Aqueous Electrolyte

A super-concentrated aqueous electrolyte, “water-in-bisalt (WiBS)”, consisting of 21 m lithium bis(trifluoromethanesulfonyl)imide and 7 m lithium trifluoromethanesulfonate on the most concentrated end, was measured for its electrolytic conductivity κ and glass transition temperature Tg in wide ranges of salt concentration m and temperature θ, with Tg as an indicator for the electrolyte viscosity. The measured κ–(m, θ) data in its entirety was fitted with an extended Casteel–Amis equation for an accurate functional representation, and the κ–θ data for the most concentrated electrolytes were fitted with the Vogel–Fulcher–Tammann equation for an evaluation of the activation energy Ea and vanishing mobility temperature T0. The resultant values of κ and T0 are compared and correlated with Tg, and the possibility of the formation of a water–salt liquid structure under these super-concentrated environments is discussed.