(155b) Quantifying the Effects of Dielectric Constant on Ion Dissociation in LiCl Electrolytes

The development of next generation separation technologies requires a fundamental understanding of a diverse range of complex electrolyte systems. Ion dissociation (often referred to as “ionicity”), which describes the extent to which cations and anions exist as individual “free” species in electrolyte systems provides a powerful metric connecting molecular-level interactions to the electrochemical and thermophysical performance of these technologies. While it is widely accepted that solvent polarity (i.e., dielectric constant) plays an important role on ionicity, a comprehensive understanding of the influence of electrolyte polarity remains elusive.

In this present study, we employ a combined experimental and theoretical approach in order to quantify the effects of dielectric constant on the ionicity and transport behavior of ternary ethanol, water, lithium chloride (LiCl) electrolytes. We leverage state-of-the-art pulse field gradient (PFG) NMR, electrophoretic NMR (eNMR), and molecular simulation techniques to probe ion and solvent self-diffusivities and electrophoretic mobilities across a range of water and ethanol compositions. By controlling the solvent (water/ethanol) compositions we are able to selectively tune the electrolyte dielectric constant and systematical investigates its role on electrolyte transport and thermodynamics. These findings provide important fundamental insights for the design of a range of energy storage, water treatment, and chemical separation technologies.