When 10:15 AM - 11:30 AM Oct 21, 2022
Where 1670 Beyster
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"Critical Electrochemical Limits on Rechargeable Alkali Metal Batteries"

Peng Bai
Washington Univeristy (St. Louis)


Next-generation high-energy batteries require rechargeable metal anodes, but hazardous dendrites tend to form during recharging, causing short-circuit risk and capacity loss. Metal dendrits can even penetrate hard and stiff ceramic electrolytes, by mechanisms that remain elusive. In this seminar, we will introduce a rigorous analysis of the lithium dendrite formation in liquid electrolytes, through the intimate combination of operando microscopy and novel transport models. Our results demonstrated the necessity to differentiate Li whiskers from Li dendrites, which are induced by different physical processes. Resolving the interfacial instability and metal whiskers led to ideally smooth, non-porous, ingot-type Na metal plating, which enabled the anode-free Na metal full cells with a record-high retention rate of 99.93% per cycle at 3C charge and discharge. Chronopotentiometry tests of this ideal metal electrode revealed an inverse correlation between the penetration overpotential and the pore size of the separator, which can be captured by a new model we named as the Young-Laplace critical overpotential. Electrochemical tests of highly consistent miniature solid-state cells confirmed a similar ion polarization and dendrite initiation mechanism in garnet-type cubic Li7-xLa3Zr2-xTaxO12 ceramic electrolytes. Our theoretical and experimental discoveries suggest that the success of alkali metal batteries relies on the rational control of both the interfacial kinetics and the bulk ion transport.


Dr. Bai obtained his Bachelor’s degree in Automotive Engineering and PhD degree in Mechanical Engineering from Tsinghua University in Beijing, China, in 2007 and 2012, respectively. He completed his postdoctoral training in the Department of Chemical Engineering at MIT, prior to joining Washington University in St. Louis as a tenure-track Assistant Professor in the Department of Energy, Environmental and Chemical Engineering in 2017. His research group is specialized in combining mesoscale operando microscopy with physics-based mathematical models to achieve precision understanding and rational engineering of battery electrodes and electrolytes. Dr. Bai has published in scientific journals including Science, Energy & Environmental Science, Joule, Advanced Energy Materials, Nature Communications, Nano Letters, etc. He won the Oronzio and Niccolò De Nora Foundation Young Author Prize from the International Society of Electrochemistry (ISE) in 2014, and the Prize for Electrochemical Materials Science from ISE in 2018. He received the NSF Career Award in 2021.