Effect of lithium bis (trifluoromethylsulfonyl) imide on the hightemperature behavior of LiFePO4 positive electrode

Haiying Che, Jun Yang*, Kai Wu, Jiulin Wang, Yanna Nuli

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The effect of lithium salts in electrolytes on the high-temperature performance of LiFePO4 electrode is investigated systematically and the related mechanism is revealed. Differential scanning calorimetry measurements show that lithium bis (trifluoromethylsulfonyl) imide (LiTFSI) and LiBF4 are more favorable for the use at high temperature than LiPF6 because of their water insensitivities and excellent thermal stabilities. Inductively coupled plasma is used to examine the dissolving degree of ferrous ions from LiFePO4 in the different electrolytes at 55°C. It is found that little ferrous ions can be dissolved from LiFePO4 in LiTFSI and fluorine-free lithium salt electrolytes. On the contrary, it is quite serious in LiPF6 electrolyte. In addition, FePO4 is easier to release iron ions than LiFePO4 in the LiPF6 electrolyte. The experimental results of cyclic voltammetry and light microscope indicate that a small amount of LiBF4 can inhibit the corrosion of aluminum foil current collector from LiTFSI. The electrolyte containing mixed salts of LiTFSI and LiBF4 significantly improves the high-temperature performance of LiFePO4/Li cell. The discharge capacity is still 147.7 mAh/g after 40 cycles at 55°C and 1 C rate.

Original languageEnglish
Pages (from-to)1287-1292
Number of pages6
JournalActa Chimica Sinica
Volume69
Issue number11
Publication statusPublished - 14 Jun 2011
Externally publishedYes

Keywords

  • Electrolyte
  • Hightemperature performance
  • Iron dissolution
  • LiFePO
  • Lithium bis (trifluoromethylsulfonyl) imide

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