Studying Novel Electrolytes for Zinc Electrochemical Technologies using NMR and MRI

Abstract

This thesis investigates novel electrolytes for zinc electroplating using NMR and MRI. Three systems have been investigated, two ChCl-based deep eutectic solvents, ethaline and reline, and the ionic liquid [C2C1Im(TfO)]. Previously, these three electrolytes have been investigated as alternative electrolytes for electroplating Zn. They have also shown promise as electrolytes for different Zn electrochemical technologies such as zinc-based batteries. A range of ethaline and reline DESs and [C2C1Im(TfO)] IL have been investigated, in the presence and absence of Zn and water. Molecular interactions and dynamics in these systems have been investigated using 1D NMR measurements such as spectroscopy, relaxation, and diffusion. These NMR relaxation studies have been used as a foundation to visualize the electroplating of zinc from Zn(TfO)2-[C2C1Im(TfO)] systems (in operando) and ZnCl2-ethaline (in situ), using MR relaxation maps. 19F MRI of the TfO anion, in the 0.15 M Zn(TfO)2-[C2C1Im(TfO)] systems, has revealed changes in both T1 and T2 during the electroplating of zinc. To understand the causes of these changes in relaxation times, we need to consider the influence of Zn and water on the relaxation time of the TfO anion. It has been observed that 19F T1 and T2 MR relaxation times are affected by the concentrations of zinc and water. The electroplating of zinc from ZnCl2-ethaline systems was imaged using 1H MR T2 relaxation time, in situ, before and after electroplating, which was performed outside the magnet. The influence of water and zinc on 1H NMR relaxation times has been used as a key for interpreting MRI results.