Ionic liquids have been proposed as candidate electrolytes for high-energy density, rechargeable batteries. We present an extensive computational analysis supported by experimental comparisons of bulk and interfacial properties of three of these electrolytes ([pyr14][TFSI], [pyr13][FSI], and [EMIM][BF4]) as a function of Li-salt doping. We begin by investigating the bulk electrolyte using quantum chemistry and ab initio molecular dynamics to elucidate the solvation structure of Li+. MD simulations using APPLE&P were then performed, from which we have obtained an array of thermodynamic and transport properties. Excellent agreement was found between the computations and experiments for diffusion, ionic conductivity, and viscosity. Combining MD simulations with electronic structure calculations, we have computed the electrochemical window of the electrolytes across a range of Li+-doping levels and comment on the role of the liquid environment. Finally, we performed a suite of simulations of these Li-doped electrolytes at ideal electrified interfaces to evaluate the differential capacitance and the equilibrium Li+ distribution in the double layer. The magnitude of differential capacitance was found to be in good agreement with our experiments and to exhibit the characteristic camel-shaped profile. In addition, the simulations revealed Li+ to be highly localized to the second molecular layer of the double layer, which was supported by additional computations that found this layer to be a free energy minimum with respect to Li+ translation.

Li-doped ionic liquid electrolytes: From bulk phase to interfacial behavior

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.