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Effect of Hydrofluoroether Cosolvent Addition on Li Solvation in Acetonitrile-Based Solvate Electrolytes and Its Influence on S Reduction in a Li–S Battery

See, Kimberly A. and Wu, Heng-Liang and Lau, Kah Chun and Shin, Minjeong and Cheng, Lei and Balasubramanian, Mahalingam and Gallagher, Kevin G. and Curtiss, Larry A. and Gewirth, Andrew A. (2016) Effect of Hydrofluoroether Cosolvent Addition on Li Solvation in Acetonitrile-Based Solvate Electrolytes and Its Influence on S Reduction in a Li–S Battery. ACS Applied Materials & Interfaces, 8 (50). pp. 34360-34371. ISSN 1944-8244. doi:10.1021/acsami.6b11358.

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Li–S batteries are a promising next-generation battery technology. Due to the formation of soluble polysulfides during cell operation, the electrolyte composition of the cell plays an active role in directing the formation and speciation of the soluble lithium polysulfides. Recently, new classes of electrolytes termed “solvates” that contain stoichiometric quantities of salt and solvent and form a liquid at room temperature have been explored due to their sparingly solvating properties with respect to polysulfides. The viscosity of the solvate electrolytes is understandably high limiting their viability; however, hydrofluoroether cosolvents, thought to be inert to the solvate structure itself, can be introduced to reduce viscosity and enhance diffusion. Nazar and co-workers previously reported that addition of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) to the LiTFSI in acetonitrile solvate, (MeCN)_2–LiTFSI, results in enhanced capacity retention compared to the neat solvate. Here, we evaluate the effect of TTE addition on both the electrochemical behavior of the Li–S cell and the solvation structure of the (MeCN)_2–LiTFSI electrolyte. Contrary to previous suggestions, Raman and NMR spectroscopy coupled with ab initio molecular dynamics simulations show that TTE coordinates to Li^+ at the expense of MeCN coordination, thereby producing a higher content of free MeCN, a good polysulfide solvent, in the electrolyte. The electrolytes containing a higher free MeCN content facilitate faster polysulfide formation kinetics during the electrochemical reduction of S in a Li–S cell likely as a result of the solvation power of the free MeCN.

Item Type:Article
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URLURL TypeDescription Information
See, Kimberly A.0000-0002-0133-9693
Shin, Minjeong0000-0002-9656-2651
Curtiss, Larry A.0000-0001-8855-8006
Gewirth, Andrew A.0000-0003-4400-9907
Additional Information:© 2016 American Chemical Society. Received: September 7, 2016. Accepted: November 16, 2016. Published: November 16, 2016. This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. K.A.S. acknowledges postdoctoral funding from the St. Elmo Brady Future Faculty Fellowship. The authors thank Lingyang Zhu for assistance with T_1 measurements and Paul M. Bayley for helpful discussions. K.C.L. and L.A.C. acknowledge grants of computer time through IBM BlueGene/Q computer through the Argonne Leadership Computing Facility (ALCF) and the LCRC Blues Cluster at Argonne National Laboratory. We thank Professor Scott E. Denmark and Guanqun Zhang of the Department of Chemistry at UIUC for the Karl Fisher titration measurements. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. Author Contributions -- K.A.S. and H.L.W.: These authors contributed equally to this work. The authors declare no competing financial interest.
Funding AgencyGrant Number
St. Elmo Brady Future Faculty FellowshipUNSPECIFIED
Department of Energy (DOE)DE-AC02-06CH11357
Subject Keywords:hydrofluoroether cosolvent; in situ Raman spectroscopy; lithium−sulfur battery; solvate electrolyte; sulfur reduction kinetics
Issue or Number:50
Record Number:CaltechAUTHORS:20180608-094332106
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Official Citation:Effect of Hydrofluoroether Cosolvent Addition on Li Solvation in Acetonitrile-Based Solvate Electrolytes and Its Influence on S Reduction in a Li–S Battery Kimberly A. See, Heng-Liang Wu, Kah Chun Lau, Minjeong Shin, Lei Cheng, Mahalingam Balasubramanian, Kevin G. Gallagher, Larry A. Curtiss, and Andrew A. Gewirth ACS Applied Materials & Interfaces 2016 8 (50), 34360-34371 DOI: 10.1021/acsami.6b11358
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86912
Deposited By: George Porter
Deposited On:08 Jun 2018 23:20
Last Modified:15 Nov 2021 20:43

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