Ionic Liquid Electrolytes for Safer Lithium Batteries

In this paper we report on the investigation of ionic liquid-based electrolytes with enhanced characteristics. In particular, we have studied ternary mixtures based on the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt and two ionic liquids sharing the same cation ( N -methyl- N -propyl pyrrolidinium, PYR 13 ), but different anions, bis(trifluoromethanesulfonyl)imide (TFSI) and bis(fluorosulfonyl)imide (FSI). The LiTFSI-PYR 13 TFSI-PYR 13 FSI mixtures, found to be ionically dissociated, exhibit better ion transport properties (about 10 −3 S cm −1 at −20°C) with respect to similar ionic liquid electrolytes till reported in literature. An electrochemical stability window of 5 V is observed in carbon working electrodes. Preliminary battery tests confirm the good performance of these ternary electrolytes with high-voltage NMC cathodes and graphite anodes. Ionic liquid electrolyte mixtures, PYR 13 TFSI, PYR 13 FSI.