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  4. Toward in-situ protected sulfur cathodes by using lithium bromide and pre-charge
 
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2017
Journal Article
Title

Toward in-situ protected sulfur cathodes by using lithium bromide and pre-charge

Abstract
Lithium-sulfur (Li-S) batteries suffer from the dissolution of its intermediate charge products (polysulfides) in organic electrolytes, which limits the utilization, rate performance and cycling stability of S cathode materials. Formation of protective surface coatings on S cathodes may effectively overcome such a challenge. Here, we explored a simple, low cost, and widely applicable method that offers in-situ formation of a protective coating on the S-based cathode by using lithium bromide (LiBr) as a novel electrolyte additive. Quantum chemical (QC) studies suggested that pre-cycling a S cathode at high potentials is needed to oxidize the Br- and induce formation of DME(-H) radicals, which are involved in the formation of a polymerized protective layer of a solid electrolyte interphase (SEI) on a S cathode at high potentials. Experimental studies with a LiBr additive confirmed that 3 pre-cycles in a voltage range of 2.5-3.6 V are sufficient to achieve the formation of a robust Li ion permeable SEI on the cathode, effectively preventing the dissolution of polysulfides into electrolyte. As a result, almost no degradation was observed within 200 cycles, compared to more than 40% of capacity loss in the benchmark control cells without LiBr or the pre-cycles. Post-mortem analysis on both the cathode and anode sides of the LiBr-comprising cells further provided evidence for the in-situ SEI formation on the cathode and the lack of polysulfides' re-precipitation. In addition, such studies showed smooth surface on the cycled Li metal anode, in contrast to the rough Li SEI with dendrites and polysulfides in the benchmark cells.
Author(s)
Wu, Feixiang
Georgia Institute of Technology
Thieme, Sören
Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS  
Ramanujapuram, Anirudh
Georgia Institute of Technology
Zhao, Enbo
Georgia Institute of Technology
Weller, Christine
TU Dresden
Althues, Holger  
Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS  
Kaskel, Stefan  
Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS  
Borodin, Oleg A.
US Army Research Laboratory
Yushin, Gleb N.
Georgia Institute of Technology
Journal
Nano energy  
Project(s)
StaLiS
Funder
Bundesministerium für Bildung und Forschung BMBF (Deutschland)  
DOI
10.1016/j.nanoen.2017.08.012
Additional full text version
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Language
English
Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS  
Keyword(s)
  • electrolyte additive

  • lithium bromide

  • polysulfide

  • core-shell nanoparticles

  • Sulfur

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