Identifying Electrolyte Reaction Mechanisms at Battery Electrodes Toward PFAS-Free Electrolytes
Jeffrey Lopez, Department of Chemical and Biological Engineering, Northwestern University
While lithium-based battery technologies are becoming increasingly widespread in our energy landscape, both in electric vehicles and grid-scale storage, there is a continued need to increase energy density, reduce costs, and improve the sustainability of their manufacturing. Lithium metal batteries offer great promise for higher energy density but have not yet met the stringent safety requirements and high efficiency required for deployment in commercial applications. Highly fluorinated ether electrolytes are often employed to address these challenges through modification of electrolyte reactivity and ion solvation structure to improve Coulombic efficiency. However, these PFAS molecules pose environmental and health concerns that should be considered when designing electrolytes for mass production.
In this presentation, I will discuss our group’s efforts to understand the mechanisms by which fluorinated electrolytes promote high-performance cycling in the context of moving toward more environmentally friendly fluorine-free electrolytes. Electron paramagnetic resonance (EPR) spectroscopy was used to identify radical reaction intermediates through a spin-trapping approach and to clarify electrolyte reduction mechanisms. Two radical compounds were identified during FEC reduction that confirm a ring-opening mechanism over other proposed pathways. With a better understanding of the role of fluorinated electrolyte species, we then developed a fluorine-free localized high concentration electrolyte (LHCE) with Coulombic efficiency greater than 99.9%. We demonstrate stable cycling of this electrolyte in full cells with thin Li metal anodes, highlighting the possibility to move away from fluorinated electrolytes through careful molecular engineering. Our work provides new insight into electrolytes for high-performance metal anodes with improved sustainability and the formation of interphase components that promote stable cycling.
Biography:
Jeffrey Lopez is an Assistant Professor of Chemical & Biological Engineering at Northwestern University. His research is focused on using fundamental chemical engineering principles to study energy storage devices and design solutions to enable accelerated adoption of sustainable energy technologies.
Prior to joining the Northwestern faculty, Jeffrey was an Intelligence Community Postdoctoral Fellow at the Massachusetts Institute of Technology and a NSF Graduate Research Fellow at Stanford University where he completed his PhD in Chemical Engineering. Jeffrey received his B.S. in Chemical Engineering from the University of Nebraska – Lincoln. Jeffrey is an expert in the study of charge transport processes and reactions at electrochemical interfaces to inform the design of new materials for energy storage applications. He is a pioneer in the area of polymer coatings to stabilize the Li metal electrodeposition and has worked extensively on the development of advanced electrolytes for various lithium-based electrode materials, and is an expert on Li metal SEI. Recently, his group has been working to discover new electrolytes for high-energy-density battery chemistries, to develop new materials and processes for more sustainable and circular battery manufacturing, and to leverage automated experimentation and high-throughput analysis to accelerate the process of materials discovery and development.
Jeffrey has received multiple awards for his research including the ECS Toyota Young Investigator Fellowship in 2025, NSF CAREER Award in 2024, ACS Henkel Award for Outstanding Graduate Research in Polymer Science and Engineering in 2020, the 2019 Metrohm Young Chemist Award, the ACS Eastman Chemical Student Award in Applied Polymer Science in 2018, and the AIChE Excellence in Graduate Polymer Research Award 1st Prize in 2016. He was also selected as a Scialog Fellow for the Automating Chemical Laboratories series. Jeffrey recently completed a Searle Teaching Fellowship at Northwestern, a program to foster teaching excellence among early career faculty, during the 23-’24 academic year.