Lithium Bis(fluorosulfonyl)imide

White to Almost white powder to crystal with Molecular Crystal Electrolytes with High Lithium Ion Conductivity.

Lithium bis(fluorosulfonyl)imide(LiFSI) is a important high-performance electrolyte material in new energy devices such as lithium-ion batteries and supercapacitors. It has the advantages of high stability (no decomposition below 200°C), excellent low temperature performance, good hydrolytic stability and environmental friendliness, etc., as the next generation of lithium hexafluorophosphate electrolyte lithium salt for secondary lithium ion batteries.

Lithium bis(fluorosulfonyl)imide is a promising new electrolyte additive for lithium ion batteries showing increased conductivity over LiPF6. Bis(fluorosulfonyl)imide has also been tested in next generation gel polymer electrolytes with improved safety properties.

Lithium bis(fluorosulfonyl)imide (LiFSI) was synthesized by a metathesis reaction between KFSI and LiBF4 in DMC in nearly quantitative yield, similar to the preparation of its analogue, lithium (fluorosulfonyl) (pentafluoroethanesulfonyl)imide (LiFPFSI).
DOI: https://doi.org/10.1016/j.jpowsour.2010.12.040

The conventional electrolytes for Li-ion batteries are based on the LiPF6 salt and carbonate solvents, lithium bis(fluorosulfonyl)imide (LiFSI) is an interesting candidate. LiFSI has an excellent solubility, and by use of concentrated electrolytes, corrosion of the aluminium current collector on the cathode side can be avoided^[1].

[1] Asheim, K., Wagner, N. P., Vullum, P. E., Foss, C. E. L., Mæhlen, J. P., & Svensson, A. M. (2025). Effect of Concentration of Lithium Bis(fluorosulfonyl)imide on the Performance of Silicon Anodes for Li-Ion Batteries. Electrochemical Science Advances, 6 1. https://doi.org/10.1002/elsa.70009