Conductivities of Lithium Tris(trifluoromethanesulfonyl) Methide in Aqueous and Nonaqueous Solutions at 25 degree C.
Abstract
In order to determine the solution properties of lithium tris(trifluoromethanesulfonyl) methide (LiMe) in water and the aprotic solvents acetonitrile (AN), propylene carbonate (PC), N,N-dimethylformamide (DMF), and nitromethane (MeNO2), conductance measurements have been carried out at 25 deg C. Molar conductivities at infinite dilution and ion pair association constants were obtained analyzing the experimental data with the Fuoss-Hsia conductance equation using the expansion of Fernandez-Prini and Justice with and without inclusion of the Chen effect. The results show that according to the ability of the solvents to solvate lithium ion, ion pair formation is small or non-existent in solvents with high donor number (water, PC, DMF and AN) but fairly moderate, in nitromethane. Single ion molar conductivities at infinite dilution for perchlorate, hexafluoroarsenate, hexafluorophosphate, triflate, imide and methide anions, obtained by combining our results with literature data, decrease as expected as the ionic radius increases, and with one exception are always greater than that of the lithium ion. This general trend does not however apply in water where the limiting ionic conductance of the lithium cation is greater than that of the methide anion. This anomalous behavior is attributed to significant solvation of the methide ion in water. Voltammetric measurements indicate high electrochemical stability of methide anion. Such anodic stability and the increase in the transference number of lithium ion in LiMe solutions strongly support the use of this electrolyte in high energy, high voltage lithium batteries. jg
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1996
- Accession Number
- ADA305326
Entities
People
- Charles W. Walker Jr.
- Mark Salomon
Organizations
- United States Army Research Laboratory