Composition manipulation of bis(fluorosulfonyl)imide-based ionic liquid electrolyte for high-voltage graphite//LiNi0.5Mn1.5O4 lithium-ion batteries

Purna Chandra Rath, Yi Wun Wang, Jagabandhu Patra, Bharath Umesh, Ting Ju Yeh, Shigeto Okada, Ju Li, Jeng Kuei Chang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Ionic liquids (ILs), with wide electrochemical stability window, high thermal stability, and nonvolatility, are promising electrolytes for lithium-ion batteries. Among ILs with various types of anion, bis(fluorosulfonyl)imide (FSI)-based ILs are particularly appealing owing to their high ionic conductivity, low viscosity, and great anode compatibility. However, strong corrosivity of FSI toward the Al current collector at high potential restricts their practical utilization. In this study, three strategies are implemented to overcome this limitation. Li+ fraction modulation, FSI/bis(trifluoromethyl)sulfonylimide (TFSI) molar ratio optimization, and their synergistic combination are used to achieve optimal charge–discharge of a high-voltage LiNi0.5Mn1.5O4 (LNMO) cathode with an Al substrate. The effects of the IL composition on the electrochemical properties of a graphite anode are also investigated. The proposed IL electrolyte, which lacks any organic solvents, has an optimal Li+/FSI/TFSI molar ratio and thus can effectively suppress the Al corrosion, allowing a 5-V graphite//LNMO full cell to be realized. A reversible capacity of ~ 135 mAh g−1 (based on LNMO) and a capacity retention of ~ 85% after 200 cycles are found for the full cell. This study opens a new route for FSI-based IL electrolytes in the field of high-voltage and high-safety lithium-ion battery applications.

Original languageEnglish
Article number128904
JournalChemical Engineering Journal
StatePublished - 1 Jul 2021


  • 5-V battery
  • Al corrosion
  • Battery safety
  • Electrolyte design
  • High-voltage cathode

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