Billy Johnson

"Advancing Lightweight Rechargeable Batteries: Sulfur-based Cathodes and Polymer Composite Solid Electrolytes"

Committee Members:

Prof. Gleb Yushin, Advisor, MSE

Prof. Faisal Alamgir, MSE

Prof. Meilin Liu, MSE

Prof. Rampi Ramprasad, MSE

Mohan Sanghadasa, Ph.D., US Army CCDC Aviation and Missile Center, Redstone Arsenal, AL

Abstract:

Lithium-sulfur batteries are a promising candidate for next-generation energy storage as they offer significantly greater specific (gravimetric) energy than commercial Li-ion batteries (LIBs) while utilizing earth-abundant, environmentally friendly and cheap cathode materials (sulfur). However, Li-S chemistry suffers from low electrical and ionic conductivities, extreme volume expansion and contraction upon cycling, and dissolution of the active material into the electrolyte resulting in poor cycle lifetimes. Solid-state batteries are safer than LIBs and have the potential to store more energy per unit volume by replacing graphite anodes with high capacity lithium (Li) or Li alloy anodes while also replacing flammable organic electrolytes with polymer or ceramic or composite ones, thus reducing safety concerns while improving performance. This proposal outlines the need for improvements in both Li-S and solid-state battery technologies and the exploration of their synergies. For example, due to relatively low potential of S cathodes, solid-state electrolytes would be stable against oxidation during cycling in Li-S cells. Due to the lack of solvent molecules in solid-state electrolytes, formation of polysulfides and their dissolution during cycling may also be prevented. In this proposal I focus my research on systematic studies of two relatively unexplored, yet highly scalable and low-cost methods for the formation of S/Li2S nanocomposite cathodes.  For the solid-state electrolyte portion of this work, focus is placed on understanding the Li transport, dendrite formation and chemical/electrochemical interactions of novel polymer and polymer-ceramic electrolytes based on largely unexplored chemistry.