Phase Behavior and Crystalline Phases of Ionic Liquid-Lithium Salt Mixtures with 1-Alkyl-3-methylimidazolium Salts

The thermal phase behavior of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (IM10RTFSI where R = 1, 2, or 4 for methyl, ethyl or butyl, respectively) ionic liquid binary mixtures with LiTFSI have been investigated as models for electrolytes For lithium batteries. Diverse phase behavior is found with significant variations noted from similar mixtures in which the imidazolium cations are replaced with N-alkyl-N-methylpyrrolidinium cations. The crystal structure for a (1-x) IM101TFSI-(x) LiTFSI (x = 0.50) (or 1/1 IM101TFSI/LiTFSI) phase is reported to further clarify the molecular level interactions occurring in these binary salt mixtures.