Charge-storage performance of Li/LiFePO4 cells with additive-incorporated ionic liquid electrolytes at various temperatures

Nithinai Wongittharom, Chueh Han Wang, Yi Chen Wang, George Ting Kuo Fey, Hui Ying Li, Tzi Yi Wu, Tai Chou Lee, Jeng Kuei Chang

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Butylmethylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMP-TFSI) ionic liquid (IL) with LiTFSI solute is used as a base electrolyte for Li/LiFePO4 cells. Three kinds of electrolyte additive, namely vinylene carbonate (VC), gamma-butyrolactone (γ-BL), and propylene carbonate (PC), with various concentrations are introduced. The thermal stability, flammability, and electrochemical properties of the electrolytes are investigated. At 25 °C, the additives (γ-BL is found to be the most effective) can significantly improve the capacity, high-rate performance, and cyclability of the cells. With an increase in temperature to 50 °C, the benefits of the additives gradually become insignificant. At 75 °C, the additives even have adverse effects. At such an elevated temperature, in the plain IL electrolyte (without additives), a LiFePO4 capacity of 152 mAh g-1 is found at 0.1 C. 77% of this capacity can be retained when the rate is increased to 3 C. These values are superior to those found for the additive-incorporated IL and conventional organic electrolytes. Moreover, negligible capacity loss is measured after 100 charge-discharge cycles at 75 °C in the plain IL electrolyte.

Original languageEnglish
Pages (from-to)268-275
Number of pages8
JournalJournal of Power Sources
Volume260
DOIs
StatePublished - 15 Aug 2014

Keywords

  • Additive
  • Electrolyte
  • Ionic liquid
  • Lithium battery
  • Temperature

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