Aditya S. Khair, Ph.D. Assistant Professor, Department of Chemical Engineering, Carnegie Mellon University

Charges, Forces, and Particles in Ionic Liquids

Abstract

This proposal aims to quantify electrochemical and electrokinetic transport in ionic liquids and concentrated electrolytes. These materials offer great promise for use in energy storage and conversion technologies such as ultra-capacitors or solar cells. However, an understanding of their nonequilibrium dynamics under time-dependent voltages, crucial to such applications, is lacking. We will fill this gap in knowledge by utilizing a recently developed model for the electric double layer at an ionic liquid-electrode interface to generate quantitative, experimentally testable models for electrically-driven transport in ionic liquids. Our preliminary results highlight that electrical transport phenomena in such fluids is radically different to that in commonly studied dilute systems, due to the prevalence of electrostatic correlations in ionic liquids and concentrated electrolytes. For instance, we predict electrophoretic velocity reversals — i.e., positively-charged colloids migrate to positively-polarized electrodes! — and drastically shorter time scales for diffuse charge dynamics. The work proposed here focuses on fundamental, paradigmatic electro-chemical and -kinetic phenomena: namely, electrophoresis, colloidal forces, and impedance spectroscopy, which highlight the curious and counterintuitive nature of transport in ionic liquids and concentrated electrolytes.

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