Redox Mediators that Promote Three-Dimensional Growth of Li2S on Carbon Current Collectors in Lithium-Sulfur Batteries

Controlling the electrodeposition of Li2S onto C using a redox mediator, BPI. With BPI, sulfur utilization improves in Li-S cells due to remote reduction of polysulfides to Li2S.

Scientific Achievement

Developed, from computation and experiment, redox mediators that allow 3-D growth of Li2S on carbon current collectors for greater capacity utilization in Li-S batteries

Significance and Impact

Vascularization of the current collector: conductive carbon “arteries” dominate long-range electron transport, while BPI “capillaries” circulate, mediating short-range transport and electron transfer between sulfur and carbon

Research Details

  • Guided by the Electrolyte Genome, we advanced benzo[ghi]peryleneimide (BPI) as a redox mediator for the reduction of dissolved polysulfides to Li2S
  • With BPI present, Li2S forms porous, 3-D deposits onto carbon current collectors during cell discharge, improving sulfur utilization 220 percent
  • The kinetics of Li2S electrodeposition under potentiostatic control were modeled using modified Avrami phase transformation kinetics, and showed that BPI slows down the impingement of insulating Li2S islands on carbon

Work performed at Lawrence Berkeley National Laboratory (JCESR partner) and Massachusetts Institute of Technology (JCESR collaborator) by L. C. H. Gerber, P. D. Frischmann, F. Y. Fan, S. E. Doris, X. Qu, A. M. Scheuermann, K. Persson, Y.-M. Chiang and B. A. Helms, Nano Lett. ASAP (2015).

DOI: 10.1021/acs.nanolett.5b04189

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