Novel silyl solvents as components of electrolytes for lithium-ion batteries have improved lithium ion transport and safety in comparison to the conventional carbonate solvents most in use in lithium-ion electronic devices.¹ This presentation will explore the ion transport of a variety of electrolytes composed of the silyl solvent families (generic structures shown in Figure 1): silyl glycol molecules where the number of ethylene oxide chain units on the silyl fragment has been varied as well as the number of carbons bonding the ethylene oxide chain to the silicon, and silyl nitrile molecules where the salt solvating moiety is a nitrile functionality instead of a glycol.  Electrolytes of the silyl solvents with the salts LiPF₆, LiTFSA, and LiBOB have been prepared and their variable temperature ionic conductivities measured by impedance spectroscopy.  Ionic conductivities of electrolytes at 25°C range from 1.1 to 2.5 mScm^-1 for salt concentrations at 0.8 M or 1 M.  Based on these promising ionic conductivities, we have prepared a variety of solvent blend electrolytes in which the silyl solvent is mixed with conventional battery solvents such as the cyclic carbonates ethylene carbonate (EC) or propylene carbonate (PC), linear carbonates ethyl methyl carbonate or diethyl carbonate, and γ-valerolactone or methyl butyrate.  In general, ionic conductivities of the silyl solvent/carbonate blend electrolytes increase in comparison to the comparable electrolyte of the pure silyl solvent achieving ionic conductivities at 25°C of 5-6 mScm^-1.  We have also measured variable temperature lithium and anion diffusion in PFG-STE NMR experiments which yield lithium and anion transference numbers.  Lithium transference numbers in silyl electrolytes are higher than those in analogous cyclic carbonate electrolytes.  From both the ionic conductivity and NMR diffusion measurements, we have calculated the extent of ion dissociation in these electrolytes.  We will report on the trend for lithium transference numbers and ion dissociation over the temperature range of 300 to 330 K for a number of electrolyte blends.  We also report the viscosities, glass transition temperatures, and dielectric constants of the silyl solvents which impact the variations in ion transport we find for the lithium salt electrolytes.  Full carbon/lithium cells of some of these electrolytes have been prepared and cycle well. 

¹L. Zhang, L. Lyons, J. Newhouse, Z.  Zhang, M. Straughan, Z. Chen, K. Amine, R. Hamers, and R. West J. Mater. Chem., 2010, 20, 8224-8226.