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Title: Effect of Anion Size on Conductivity and Transference Number of Perfluoroether Electrolytes with Lithium Salts

Abstract

Mixtures of perfluoropolyethers (PFPE) and lithium salts with fluorinated anions are a new class of electrolytes for lithium batteries. Unlike conventional electrolytes wherein electron-donating oxygen groups interact primarily with the lithium cations, the properties of PFPE-based electrolytes appear to be dependent on interactions between the fluorinated anions and the fluorinated backbones. We study these interactions by examining a family of lithium salts wherein the size of the fluorinated anion is systematically increased: lithium bis(fluorosulfonyl)imide (LiFSI), bis(trifluoromethanesulfonyl)imide (LiTFSI) salts and lithium bis(pentafluoroethanesulfonyl)imide (LiBETI). Two short chain perfluoroethers (PFE), one with three repeat units, C6-DMC, and another with four repeat units, C8-DMC were studied; both systems have dimethyl carbonate end groups.We find that LiFSI provides the highest conductivity in both C6-DMC and C8-DMC. These systems also present the lowest interfacial resistance against lithium metal electrodes. The steady-state transference number (t + ss) was above 0.6 for all of the electrolytes and was an increasing function of anion size. The product of conductivity and the steady-state transference number, a convenient measure of the efficacy of the electrolytes for lithium battery applications, exhibited a maximum at about 20 wt% salt in all electrolytes. Finally, amongst the systems studied, LiFSI/PFE mixtures were the most efficaciousmore » electrolytes.« less

Authors:
ORCiD logo [1];  [2];  [1];  [2];  [3];  [4]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Chemical and Biomolecular Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division
  2. Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry
  3. Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Technologies Division
  4. Univ. of California, Berkeley, CA (United States). Dept. of Chemical and Biomolecular Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Technologies Division
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1476456
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 164; Journal Issue: 14; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Li ion transport; Perfluoropolyether; transference number

Citation Formats

Shah, Deep B., Olson, Kevin R., Karny, Adar, Mecham, Sue J., DeSimone, Joseph M., and Balsara, Nitash P. Effect of Anion Size on Conductivity and Transference Number of Perfluoroether Electrolytes with Lithium Salts. United States: N. p., 2017. Web. doi:10.1149/2.0301714jes.
Shah, Deep B., Olson, Kevin R., Karny, Adar, Mecham, Sue J., DeSimone, Joseph M., & Balsara, Nitash P. Effect of Anion Size on Conductivity and Transference Number of Perfluoroether Electrolytes with Lithium Salts. United States. doi:10.1149/2.0301714jes.
Shah, Deep B., Olson, Kevin R., Karny, Adar, Mecham, Sue J., DeSimone, Joseph M., and Balsara, Nitash P. Wed . "Effect of Anion Size on Conductivity and Transference Number of Perfluoroether Electrolytes with Lithium Salts". United States. doi:10.1149/2.0301714jes. https://www.osti.gov/servlets/purl/1476456.
@article{osti_1476456,
title = {Effect of Anion Size on Conductivity and Transference Number of Perfluoroether Electrolytes with Lithium Salts},
author = {Shah, Deep B. and Olson, Kevin R. and Karny, Adar and Mecham, Sue J. and DeSimone, Joseph M. and Balsara, Nitash P.},
abstractNote = {Mixtures of perfluoropolyethers (PFPE) and lithium salts with fluorinated anions are a new class of electrolytes for lithium batteries. Unlike conventional electrolytes wherein electron-donating oxygen groups interact primarily with the lithium cations, the properties of PFPE-based electrolytes appear to be dependent on interactions between the fluorinated anions and the fluorinated backbones. We study these interactions by examining a family of lithium salts wherein the size of the fluorinated anion is systematically increased: lithium bis(fluorosulfonyl)imide (LiFSI), bis(trifluoromethanesulfonyl)imide (LiTFSI) salts and lithium bis(pentafluoroethanesulfonyl)imide (LiBETI). Two short chain perfluoroethers (PFE), one with three repeat units, C6-DMC, and another with four repeat units, C8-DMC were studied; both systems have dimethyl carbonate end groups.We find that LiFSI provides the highest conductivity in both C6-DMC and C8-DMC. These systems also present the lowest interfacial resistance against lithium metal electrodes. The steady-state transference number (t+ss) was above 0.6 for all of the electrolytes and was an increasing function of anion size. The product of conductivity and the steady-state transference number, a convenient measure of the efficacy of the electrolytes for lithium battery applications, exhibited a maximum at about 20 wt% salt in all electrolytes. Finally, amongst the systems studied, LiFSI/PFE mixtures were the most efficacious electrolytes.},
doi = {10.1149/2.0301714jes},
journal = {Journal of the Electrochemical Society},
number = 14,
volume = 164,
place = {United States},
year = {2017},
month = {11}
}

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Works referenced in this record:

A review of the features and analyses of the solid electrolyte interphase in Li-ion batteries
journal, September 2010