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

Journal Article · · Journal of the Electrochemical Society
DOI:https://doi.org/10.1149/2.0301714jes· OSTI ID:1476456
 [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
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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.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1476456
Alternate ID(s):
OSTI ID: 1470279
Journal Information:
Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 14 Vol. 164; ISSN 0013-4651
Publisher:
The Electrochemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (6)

Fluor und Lithium: Ideale Partner für Elektrolyte in wiederaufladbaren Hochleistungsbatterien journal July 2019
Fluorine and Lithium: Ideal Partners for High‐Performance Rechargeable Battery Electrolytes journal November 2019
Morphological effects on polymeric mixed ionic/electronic conductors journal January 2019
Multivalent ion conduction in solid polymer systems journal January 2019
Difference between approximate and rigorously measured transference numbers in fluorinated electrolytes journal January 2019
Ohm’s law for ion conduction in lithium and beyond-lithium battery electrolytes journal July 2019

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Related Subjects

25 ENERGY STORAGE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Li ion transport
Perfluoropolyether
transference number