The aqueous electrolyte system of lithium bis­(trifluoromethanesulfonyl)­imide, LiTFSI–H2O, was systematically and accurately measured for a complete liquid–solid phase diagram and an extensive set of data on electrolytic conductivity and glass-transition temperature. The conductivity data set was fitted with a VFT-based function (VFT: Vogel–Fulcher–Tammann), of which the three parameters were set to Laurent polynomial functions of composition. The fitting results were correlated with other quantities, and comparisons were made between the results of this study and those of other aqueous and carbonate electrolyte systems. The results of these measurements, correlations, and comparisons strongly suggest a decoupling of cationic conduction from the movement of the bulk solution, in sharp contrast to what has been observed in any nonaqueous electrolytes so far.