Modulating Entropic Driving Forces to Promote High Lithium Mobility in Solid Organic Electrolytes
Jack McAlpine, Alex Bloemendal, Jeremy Dahl, Robert M. K. Carlson, Ilia A. Guzei, Catherine F. M. Clewett, Boryslav O. Tkachenko, Peter R. Schreiner, Matthew A. Gebbie
Abstract
As large-scale lithium-ion battery deployment accelerates, continued use of flammable organic electrolytes exacerbates issues associated with battery fires during operation and disposal. While ionic liquid-derived electrolytes promise safe, nonflammable alternatives to carbonate electrolytes, the use of ionic liquids in batteries is hindered by poor lithium transport due to the formation of long-lived lithium–anion complexes. We report the design and characterization of novel ionic liquid-inspired organic electrolytes that leverage unique self-assembly properties of molecular diamond templates, called “diamondoids”. Combining thermodynamic characterization, vibrational and magnetic spectroscopy, and single-crystal X-ray analysis, we determine that diamondoid-functionalized cations can facilitate the formation of molecularly porous phases that resist restructuring upon dissolution of lithium salts. These electrolytes can suppress lithium–anion coordination, manifesting in substantially enhanced lithium-ion mobility in the organic ion matrix. Our results provide a new paradigm for enhancing lithium mobility in solid electrolytes by tuning entropic self-assembly to enhance organic cation–anion interactions, suppress lithium–anion coordination, and increase lithium mobility in solid electrolytes.