Comparative study on the ionic conductivities and redox properties of LiPF6 and LiTFSI electrolytes and the characteristics of their rechargeable lithium ion batteries

Abstract

The ionic conductivities of two different electrolytes, namely lithium hexafluorophosphate (LiPF6) and lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), in carbonate-based solvents have been investigated. The ionic conductivity of LiTFSI electrolyte is slightly larger than the LiPF6 electrolyte, namely 2.7 mS/cm vs. 2.4 mS/cm. The results of cyclic voltammetry and electrochemical impedance spectroscopy measurements show that LiTFSI electrolyte exhibit a better reversible redox reaction. Therefore, in this work, the full-cell battery using LiTFSI electrolyte exhibited higher specific capacity than the battery cell using LiPF6 electrolyte, namely 83.1 mAh/g and 101.5 mAh/g for the LiPF6 and LiTFSI electrolytes, respectively. Higher capacity in LiTFSI battery is thus related to better ionic conductivity and reversible redox reaction of LiTFSI electrolyte.