(602c) Mixtures on Graphite Surfaces for Battery Electrolytes

Traditional electrolytes, such as organic carbonates, suffer from flammability and limited stability at high voltages, posing safety and performance challenges for existing batteries. Ionic liquids have emerged as promising alternatives due to their low vapor pressure and high thermal, chemical, and electrochemical stability. As many ionic liquids suffer from high viscosity and low ionic conductivity, ionic liquid mixtures comprising of ionic liquid-ionic liquid and ionic liquid-solvent mixtures provide a promising route to enhance the transport characteristics of such systems. The overall performance of batteries containing these mixture systems will additionally be governed by the interfacial structures of various species. However, there is currently a gap in the knowledge regarding preferential adsorption of various species at electrode surfaces. In this presentation, we will discuss our work on employing molecular dynamics simulations to investigate the interfacial behavior of imidazolium-based binary ionic liquid mixtures on various graphite surfaces. In particular, we will consider the system consisting of the common cation 1-ethyl-3-methylimidazolium [C₂mim]⁺ and binary mixtures of the anions: tetrafluoroborate [BF₄]^- and bis(trifluromethanesulfonyl)imide [NTf₂]^-. We will present our results in terms of number density profiles normal to the graphite surface to identify the nature of adsorbed species. We will also elucidate the orientation of the cation with respect to the graphite surface and show how the transport properties of the cation and anion are affected as a function of the distance from the interface. We will discuss the implication of the molecular structure and dynamics, in the presence of various graphite surfaces, on the overall battery performance.