[CCoE Notice] Seminar: Pristine or Highly Defective? Understanding the Role of Graphene Structure for Stable Lithium Metal Plating * MH 180, Bauer Business School * 10:30 am, Friday, September 6, 2019 * David Mitlin * The University of Texas at Austin *

[Knudsen, Rachel W]

***** Seminar *****
Department of Electrical and Computer Engineering
Materials Engineering Program
Center for Integrated Bio and Nano Systems
  September 6, 2019
10:30 a.m., Room: MH 180
Pristine or Highly Defective? Understanding the Role of Graphene Structure for Stable Lithium Metal Plating
David Mitlin
Walker Department of Mechanical Engineering
The University of Texas at Austin, Austin, Texas
Abstract:. We are the first to examine the role of graphene host structure/chemistry in plating-stripping in lithium metal anodes employed for lithium metal batteries (LMBs). Structural and chemical defects are bad since highly defective graphene promotes unstable solid electrolyte interphase (SEI) growth. This consumes the FEC additive in the carbonate electrolyte and is correlated with rapid decay in CE and formation of filament-like Li dendrites. A unique flow-aided sonication exfoliation method is employed to synthesize "defect-free" graphene (df-G), allowing for a direct performance comparison with conventional reduced graphene oxide (r-GO). At cycle 1, the r-GO is better electrochemically wetted by Li than df-G, indicating that initially it is more lithiophilic. With cycling, the nucleation overpotential with r-GO becomes higher than with df-G, indicating less facile plating reactions. The df-G yields state-of-the-art electrochemical performance; stable plating at 0.5 - 4 mA/cm2, areal capacity up to 2 mAh/cm2, cycle 1 CE at 98% and cycle 100 CE at 94%. With df-G the post cycled metal surface is relatively smooth and dendrite-free. Conversely, r-GO templates have CE rapidly degrade from the onset, with extensive dendrites after cycling. Extensive SEI growth and associated FEC depletion with r-GO are further confirmed by electrochemical impedance analysis and surface science methods (XPS). We therefore propose the following design rule for next-generation supports for LMBs: An ideal architecture will promote copious heterogenous nucleation of the plating metal, shielding it from the electrolyte. In addition, it is essential that the host is itself non-catalytic towards SEI formation.
Bio: David Mitlin is a David Allen 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. Dr. Mitlin has published about 150 peer-reviewed journal articles on various aspects of energy storage materials and on corrosion – fouling phenomena. This work is cited at near 2000 times per year. Dr. Mitlin holds 5 granted U.S. patents and 13 more pending full applications, with all of them licensed currently or in the past. He has presented 125 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. Dave received a Doctorate in Materials Science from U.C. Berkeley in 2000, M.S. from Penn State in 1996, and B.S. from RPI in 1995. He grew up in upstate NY and in southern CT.
Contact Prof. Yan Yao (yyao at central.uh.edu<mailto:yyao at central.uh.edu>)   if you would like to meet with Dr. Mitlin.
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