Lithium metal battery systems (LMBs) are being sought as an ultimate replacement to LIBs, potentially increasing the cell energy by over fifty percent due to the high capacity and low voltage of the metal anode. Analogous improvement in energy is possible with sodium metal batteries (NMBs) and with potassium metal batteries (KMBs), where existing ion insertion anodes can be replaced by plating/stripping metal. However, in all three cases safety and performance are compromised by an unstable solid electrolyte interphase (SEI) that consumes metal ions and electrolyte, and ultimately leads to dendrites. This presentation provides a series of case studies derived from the group's LMB, NMB and KMB research on the microstructural design principles that provide for long-term cycling and fast-charge stability of metal anodes. The approaches may be categorized as the following: a) design of plating/stripping supports and templates with tuned geometry and functionality; b) design of secondary interlayers placed between the metal anode and the separator; and c) design of multifunctional hybrid separators to replace the conventional polymer separators employed with LIBs. It is demonstrated that despite appearing distinct, the efficacy of each in enabling electrochemical stability originates from three fundamental features that are directly interrelated. The wetting behavior of the electrolyte on the anode must be optimized, the wetting/stripping behavior of the metal anode on the current collector must be controlled, and a geometrically and chemically modified SEI must be established. Simultaneously achieving all three leads to stable plating/stripping, while missing even one leads to rapid dendrite growth. Cryogenic FIB cross sections and cryo-TEM are combined to yield new insight regarding film wetting behavior and early dendrite formation in optimized versus baseline specimens, analyzing growth in several representative electrolytes.
David Mitlin is a Cockrell Endowed Professor at the Walker Department of Mechanical Engineering, The University of Texas at Austin. Prior to that, he was a Professor and General Electric Chair at Clarkson University, and an Assistant, Associate and full Professor at the University of Alberta, Alberta Canada. Dr. Mitlin is an ISI Highly Cited Researcher, having published about one hundred and seventy-five journal articles on various aspects of energy storage materials, metallurgy and corrosion. He also holds fifteen granted U.S. patents and eighteen more pending full applications, with all of them licensed currently or in the past. He has presented over one hundred invited, keynote and plenary talks at various international conferences. Dr. Mitlin is an Associate Editor for Sustainable Energy and Fuels, a Royal Society of Chemistry Journal focused on renewables. He received a Doctorate in Materials Science from U.C. Berkeley, a M.S. from the Pennsylvania State University, and a B.S. from Rensselaer Polytechnic Institute.