Speaker: Steve G. Greenbaum, Hunter College of the City University of New York
A Personal View Through Recent Liquid State and Solid State NMR Investigations of Novel Electrolytes
All major automobile companies will cease manufacturing internal combustion-powered vehicles within a timeframe measured in years rather than decades. The need for mitigating “range anxiety” without sacrificing safety presents a major challenge to present-day lithium ion technology, which has nearly reached its physical limit in energy density. New chemistries with correspondingly new materials are needed for the next generation of batteries. Replacing the graphite negative electrode with Li metal or Si/Li alloy and using low- (or zero-) cobalt cathodes are leading strategies. Sulfur-based cathodes are also under consideration. The major bottleneck in all of these current and proposed developments is the lack of a suitable electrolyte needed to eliminate the flammable liquid carbonate electrolyte solvents in use today. Among replacement candidates are low molecular mass polyethers (i.e. glymes), ionic liquids (ILs), inorganic solid electrolytes including glassy sulfides and garnet-type, and polymer electrolytes.
Our laboratory is focused on application of various nuclear magnetic resonance (NMR) techniques to help understand structure and dynamics of energy storage materials, in particular novel electrolytes. In this presentation we discuss three recent collaborative efforts.
(i) The first topic, in collaboration with Oak Ridge National Lab (R. Ruther, J. Nanda), is on low molecular mass polyethers (i.e.glyme) -based electrolytes being developed for lithium metal and Na ion batteries as well as electrolytic double layer capacitors. Though electrochemically more stable than the carbonates, NMR and vibrational spectroscopic measurements show that significant ion pairing is evident in these electrolytes.
(ii) In collaboration with UCLA (B. Dunn, D. Ashby), we have investigated ionogels, which are pseudo-solid-state electrolytes consisting of the IL BMIM TFSI plus LiTFSI salt electrolyte confined in a mesoporous inorganic matrix. We report here NMR measurements of ionic self-diffusion coefficients as well as broadband relaxometry with emphasis on elucidating confinement effects of the silica matrix on ionic transport.
(iii) Our collaborators at U. Maryland (L. Hu et.al.) have developed a cellulose-based solid electrolyte in which coordination of Cu2+ ions with the 1D cellulose nanofibrils leads to the formation of molecular channels that enable facile Li+ ion transport. We show how NMR contributed to our understanding of local structure and ion transport in this novel material.
Dr. Steve Greenbaum is CUNY Distinguished Professor of Physics at Hunter College and the CUNY Graduate Center, and a Fellow of the American Physical Society. He is also a science advisor/consultant at Ionic Materials, Inc. in Woburn, MA. He served (2008-14) as Executive Officer of the Ph.D. Program in Physics at the CUNY Graduate Center. Dr. Greenbaum earned his Ph.D. in Physics from Brown University. He spent two years at the US Naval Research Laboratory in Washington, D.C. as an NRC Postdoctoral Fellow, and spent sabbatical years as a Fulbright Scholar at the Weizmann Institute of Science, and a NASA/NRC Senior Research Fellow at the Jet Propulsion Lab, Caltech, where he was a member of the team that designed the lithium ion batteries for the successful Mars Rover missions. He has held Visiting Professorships at Stony Brook University, Rutgers University, Tel Aviv University, the University of Paris-Sud (XI), the University of Padova, and the University of Rome, La Sapienza.
Dr. Greenbaum's main research interest is magnetic resonance of disordered solids, mostly on materials for electrochemical energy storage and conversion (i.e. batteries and fuel cells). He has co-authored over 300 peer reviewed publications, and directly supervised the research of 21 postdoctoral associates, 30 Ph.D. students, and numerous BA research students.
Dr. Greenbaum was the 2001 recipient of the Roosevelt Gold Medal for Science, awarded by the United States Navy League, and the 2002 Presidential Award for Excellence in Science, Mathematics and Engineering Mentoring bestowed by the White House. He also received the 2003 Richard Nicholson Science Teaching Award. Dr. Greenbaum was one of eleven Jefferson Science Fellows who served as Senior Science advisors to the U.S. State Department in 2014-15. He was also recognized by the Society for the Advancement of Chicanos and Native Americans in Science by receiving their 2016 Distinguished Scientist Award.