Accession Number : ADA305326

Title :   Conductivities of Lithium Tris(trifluoromethanesulfonyl) Methide in Aqueous and Nonaqueous Solutions at 25 degree C.

Descriptive Note : Technical rept. Jun 95-Feb 96,

Corporate Author : ARMY RESEARCH LAB FORT MONMOUTH NJ

Personal Author(s) : Walker, Charles W., Jr. ; Salomon, Mark

PDF Url : ADA305326

Report Date : FEB 1996

Pagination or Media Count : 18

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

Descriptors :   *CONDUCTIVITY, *SOLUTIONS(MIXTURES), *LITHIUM, *NONAQUEOUS ELECTROLYTES, ANOMALIES, IONS, CATIONS, MEASUREMENT, STABILITY, EXPERIMENTAL DATA, METHYL RADICALS, ACETONITRILE, WATER, ELECTROCHEMISTRY, HIGH ENERGY, PROPENES, CONSTANTS, PATTERNS, SOLVENTS, LITHIUM BATTERIES, METHANE, ELECTROLYTES, SOLVATION, DILUTION, ANIONS, HIGH VOLTAGE, NITROMETHANE, FLUORINE COMPOUNDS, SULFONYL RADICALS, CARBONATES, ARSENATES, FORMAMIDES, SOLVATES.

Subject Categories : Inorganic Chemistry
      Organic Chemistry
      Physical Chemistry
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE