Ion transport in non-aqueous electrolyte mixtures of zinc chloride deep eutectic solvent (DES) and molecular solvents

The ion dynamics of null solvents 1ZnCl2:4EtG and 1ChCl:1ZnCl2:6EtG incorporating 1M water, propylene carbonate (PC) or acetonitrile (AcN) were investigated using 1H NMR spectra and spin-lattice relaxation time (T1) measurements combined with ionic conductivity, density, and viscosity, all as a function of temperature. Results show that the inclusion of all co-solvents increased the available free volume of the mixtures and followed the trend H2O ≤ PC < AcN. 1H NMR spectra and T1 inferred the presence of multiple ionic species with varying rates of mobilities. These dynamic heterogeneities were displayed by the broad T1 minima – especially for the 1ZnCl2:4EtG mixtures – and asymmetrically broadened linewidths. T1 results also revealed selective interaction sites between the hydrogen bond donors and acceptors, as well as with the co-solvents.