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The thermal phase behavior and ionic conductivity of mixtures of N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids (PY1RTFSI where R = 4 or 5 for butyl or pentyl) with LiTFSI have been examined as model systems for ionic liquid-based lithium battery electrolytes. Several mixed salt crystalline phases form. The ionic conductivity variability of the mixtures correlates well with the reported phase behavior. The crystal structures for the (1-x) PY1RTFSI-(x) LiTFSI (x = 0.67) (or 1/2 PY1RTFSI/LiTFSI with R = 4 or 5) phases have been determined. These phases are isostructural, consisting of ionic planar layers formed by Li+···TFSI– linkages in which the uncoordinated PY1R+ cations reside in cavities within the layers. These structures have been used to aid in correlating Raman data with cation–anion coordination in the IL-LiTFSI binary salt mixtures.

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.

The salt N-ethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR12TFSI) undergoes several solid−solid phase transitions before melting at 91 °C. At −120 °C, the crystal structure cons...

Crystal structures of glyme solvates with LiTFSI and LiBETI (TFSI- = bis(trifluoromethanesulfonyl)imide, BETI- = bis(perfluoroethanesulfonyl)imide) have been determined including (monoglyme)1:LiBETI, (diglyme)2:LiTFSI, (diglyme)1/2:LiTFSI, and low-temperature (triglyme)1:LiBETI. These solvates, combined with the phase behavior of the salts with various glymes from DSC analysis, provide insight into the molecular interactions of lithium salts in ethoxy solvents commonly used for solid polymer and liquid electrolytes. Many of the solvates appear to undergo order−disorder solid phase transitions. These are the first reported crystal structures containing the BETI- anion.

The crystal structures of PEO3:LiBF4, (diglyme)2:LiBF4, and (diglyme):LiBF4 have been determined and are compared. The helical conformation of each polymer chain and the stacking of neighboring chains in the structure of the PEO complex is similar to that found in the complexes with Li imide and Li triflate salts of the same PEO:salt ratio. Both PEO3:LiBF4 and (diglyme):LiBF4 have similar coordination around Li+, i.e., 3 ether oxygens and 2 fluorines from two BF4- anions. However, in the former each anion bridges two neighboring Li+ cations located along the PEO chain axis forming a continuous chain −BF4-−Li+−BF4-−Li+− whereas in (diglyme):LiBF4 two BF4- anions bridge between pairs of Li+ forming discrete diglyme−Li+−(BF4-)2−Li+−diglyme units that are linked to their neighbors predominantly by van der Waals bonding. The (diglyme)2:LiBF4 structure is compared with those of PEO6:LiSbF6 (no PEO6:LiBF4 exists) and (diglyme)2:LiSbF6. In both cases the Li+ cations are 6-coordinated by three ether oxygens from t...

Phase diagrams are reported for mixtures between bis(trifluoromethanesulfonyl)imide (TFSI-) salts containing Li+ and N-alkyl-N-methylpyrrolidinium (PYR1R+) cations. The latter salts readily form both room temperature ionic liquids and plastic crystalline phases. Mixed salt crystalline phases are found which are likely to influence the performance of such mixed salt systems when utilized as electrolytes for electrochemical devices as well as give insight into ionic liquid−solute interactions.

Crystalline phases of (triglyme)1:LiX (X = CF3SO3-, BF4-, ClO4-, and AsF6-) have been isolated and structurally characterized. The phases are isostructural and represent a novel form of Li+ cation coordination not observed in crystalline poly(ethylene oxide) (PEO)−salt phases. The crystal structure of a (triglyme)1:LiBPh4 phase has also been determined, which differs markedly from those found with the smaller anions. In addition, a more concentrated (triglyme)2/3:LiCF3SO3 phase has been characterized, which also displays a novel form of Li+ cation coordination. Such solvates represent models for interchain cation transport transition states in concentrated liquid and amorphous PEO electrolytes.