Revealing Mechanisms of Ion Correlations and Conductivity in Complex Ionic Systems

With support from the Chemical Structure and Dynamics (CSD) program in the Division of Chemistry, Professors Alexei Sokolov, Stephen J. Paddison, and Ivan Popov of the University of Tennessee are developing a fundamental molecular-level understanding of the effect of ionic correlations on conductivity of polymerized ionic liquids and organic ionic plastic crystals. Dramatic enhancement in conductivity is observed upon the addition of salts to these systems, but the mechanisms responsible for this increase are not well understood. This project investigates the influence of molecular parameters on ionic correlations and conductivity, with the goal of enhancing charge transport. The team will utilize a unique combination of various spectroscopies complemented with atomistic molecular dynamic simulations to study the structure and dynamics of these ionic systems across a wide range of time and length scales. Their studies will deepen fundamental understanding of collective ion dynamics in complex ionic systems and will be instrumental in the rational design of novel highly conductive electrolytes for various energy storage and conversion technologies. Students and a postdoctoral researcher involved in this project will acquire valuable experience in advanced experimental and computational research, and the PIs will also be engaged in various outreach activities targeted K-12 audiences.The project focuses on unraveling fundamental mechanisms controlling ion transport in doped polymerized ionic liquids and organic ionic plastic crystals. Experimental work will include unique combinations of various spectroscopic techniques including: Broadband Dielectric Spectroscopy, Light Scattering, Rheology, Quasielastic Neutron Scattering, and Nuclear Magnetic Resonance (NMR) spectroscopy over a very broad range in frequency. They will be combined with ab initio and classical atomistic molecular dynamics (MD) simulations and electronic structure calculations. The results of the proposed research will unravel molecular-level mechanisms that lead to an increase in ionic conductivity in doped polymerized ionic liquids and organic ionic plastic crystals, thereby enhancing fundamental understanding of strong correlations in the dynamics of concentrated ionic systems. The proposal aims to provide comprehensive insight into the role of the size, mass, mobility, and electrostatic interactions of ions in conductivity and ionic correlations in complex ionic systems. The findings will facilitate the design of novel electrolytes for various critical electrochemical technologies, including solid-state batteries and long-duration energy storage. The graduate students and a postdoctoral researcher engaged in project will acquire a thorough and fundamental understanding that will provide opportunities for subsequent involvement and/or employment in high technology professions in green and renewable energy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.