Physicochemical and electrochemical properties of the (fluorosulfonyl)(trifluoromethylsulfonyl)amide ionic liquid for Na secondary batteries

Huan Yang, Xu Feng Luo, Kazuhiko Matsumoto*, Jeng-Kuei Chang, Rika Hagiwara

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

In this study, thermal, physical, and electrochemical properties of the ionic liquid electrolyte system, Na[FTA]-[C3C1pyrr][FTA], (FTA = (fluorosulfonyl) (trifluoromethylsulfonyl)amide and C3C1pyrr+ = N-methyl-N-propylpyrrolidinium) have been investigated for Na secondary batteries. The asymmetric FTA structure provides a wide liquid-phase temperature range, especially at low x(Na[FTA]) (x(Na[FTA]) = molar fraction of Na[FTA]) and low temperature range. Glass transition at 170–209 K is the only observed thermal behavior in the x(Na[FTA]) of 0.0–0.4. Temperature dependence of viscosity and ionic conductivity obeys the Vogel‒Tammann‒Fulcher equation, and the correlation between molar conductivity and viscosity follows the fractional Walden rule. The anodic potential limits are above 5 V vs. Na+/Na at 298 and 363 K. The noticeable effects of x(Na[FTA]) are observed in the electrochemical performance of Na metal and hard carbon electrodes. In both cases, a moderate concentration, x(Na[FTA]) of 0.2–0.3, enables favorable charge-discharge behavior. At 363 K, the discharge capacities of the hard carbon electrode at x(Na[FTA]) of 0.3 are 260 and 236 mAh g−1 at the current densities of 20 and 200 mA g−1, respectively. The optimum cycling performance occurs at x(Na[FTA]) = 0.3, providing satisfactory capacity retention and high average Coulombic efficiency.

Original languageEnglish
Article number228406
JournalJournal of Power Sources
Volume470
DOIs
StatePublished - 15 Sep 2020

Keywords

  • (fluorosulfonyl)(trifluoromethylsulfonyl)amide
  • Hard carbon
  • Ionic liquids
  • Na secondary batteries

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