Structure and Dynamics of the Lithium Ion Solvation Shell in Ureas

Lithium ion batteries have become ubiquitous to modern life due to its use in the energy storage needs of our daily lives. In past several decades, much effort has been put into studying the molecular structure of electrolytes composed of organic carbonates. However, other solvents with similar properties but better thermal stabilities, such as tertiary amides, have not received the same level of scrutiny. In this work, solutions of lithium salts in ureas, tertiary amides with structure RR’N-CO-NR’’R’’’, with different sizes and connectivity are studied. Ureas present an interesting case study because unlike organic carbonates the amide bond is planar and has restricted conformational change. In addition, ureas cannot bind the lithium ion through their nitrogen atoms. By using steady-state and time-resolved infrared spectroscopies and ab-initio computational methods, detailed descriptions of the changes to the lithium ion solvation structure as a result of the urea structure were derived for three ureas b...