Understanding Ion Solvation Structure and Transport in Multicomponent Ionic Liquids

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Ionic liquids are liquid salt mixtures that have favorable physical properties such as thermal and electrochemical stability, non-flammability, and low volatility, which render them as ideal solvents, catalysts, and electrolytes in various chemical synthesis and energy storage applications. A current research need to enable wider adoption of electric cars, is high performance batteries with sufficient durability while retaining safe operations. This fundamental research project aims to introduce a control knob for the design of ionic liquids' properties as electrolytes for lithium ion and lithium metal batteries. This rational design approach may lead to the realization of safer batteries with nonflammable electrolytes operable at temperatures beyond the range of traditional electrolytes and within extremely reductive or oxidative environments where all other electrolytes fail. This project will advance the next generation of energy storage devices. As part of this project, the integrated education program 'STEAM for Energy' will enhance students' science and engineering training by teaching fundamental physical phenomena through a visual arts lens. The visual arts module will be integrated into the Case Western Reserve University curriculum through the investigators ongoing collaborations with the Cleveland Institute of Art. The expected outcomes from the educational and outreach activities are increased interest and broadened participation in STEM, and enhanced creativity and scientific communication skills for engineering students.The objective of this project is to understand the solvation structure and transport mechanism of solute ions in multicomponent ionic liquids, where ions of three or more are present. The research will utilize a theory-guided experimental approach that combines quantum calculations with Raman spectroscopy to interpret the ion coordination and solvation structure in the complex electrolytes. How the structure impacts transport properties and ultimately the system level performances will be investigated by lithium ion transference measurements and rate-capability tests. The new knowledge gained will answer important fundamental questions including the relationship among the solute ion concentration, ion coordination within the solvation structure, and the ion conductivity in multicomponent ionic liquid mixtures and the characterization and mechanism of the role of induced, polar-nonpolar, nanoscale heterogeneity of ionic liquids in determining the macroscopic conductivity and the solute ion transference. This research will produce new electrolytes and the underpinnings of the transport properties that are relevant to next generation electrochemical energy storage systems.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.