CONDUCTANCE OF SOLUTIONS OF LITHIUM TRIS(TRIFLUOROMETHANESULFONYL) METHIDE IN WATER, ACETONITRILE, PROPYLENE CARBONATE, N,N-DIMETHYLFORMAMIDE, AND NITROMETHANE AT 25-DEGREES-C

In order to determine the solution propertes of Lithium tris(trifluoro methanesulfonyl) methide (LiMe) in water and the aprotic solvents acet onitrile (AN), propylene carbonate (PC), N,N-dimethylformamide (DMF), and nitromethane (MeNO(2)), conductance measurements have been carried out at 25 degrees C. Molar conductivities at infinite dilution (Lambd a degrees) and ion pair association constants (K-a) were obtained anal yzing the experimental data with the Fuoss-Hsia conductance equation u sing the expansion of Fernandez-Prini and Justice with and without inc lusion of the Chen effect. The results show that according to the abil ity of the solvents to solvate lithium ion, ion-pair formation is smal l or nonexistent in solvents with high donor number (water, PC, DMF, a nd AN) but fairly moderate (K-a=30) in nitromethane. Single-ion molar conductivities at infinite dilution for ClO4-, AsF6-, PF6-, CF3SO3-, N (CF3SO2)(-) and C(CF3SO2)(3)(-) anions, obtained by combining our resu lts with literature data, decrease as expected as the ionic radius inc reases, and with one exception are always greater than that of the lit hium ion. This general trend does not, however, apply in water where t he limiting ionic conductance of the lithium cation is greater than th at of the methide anion. This anomalous behavior is attributed to sign ificant solvation of the methide ion in water. Voltammetric measuremen ts indicate high electrochemical stability of methide anion. Such anod ic stability and the increase in the transference number of lithium io n in LiMe solutions strongly support the use of this electrolyte in hi gh energy, high voltage lithium batteries.