Charge Transport in Nonaqueous Liquid Electrolytes: A Paradigm Shift.

摘要

We studied the temperature-dependence of mass and charge transport (ionic conductivity, self-diffusion, fluidity, and dielectric relaxation) in polar organic liquids and their electrolytes. Previous studies have described transport in terms of mutually incompatible models that provide inadequate descriptions of experimental data, often using empirical equations whose fitting parameters have no physical significance. Consequently there is no general molecular-level picture that adequately describes temperature-dependent transport in these important systems. We have developed a new approach to this problem, termed the Compensated Arrhenius Formalism (CAF). We write a transport property as an Arrhenius-like expression where the exponential prefactor is a function of the temperature-dependent static dielectric constant. We discovered a scaling procedure in which the transport coefficient is scaled to a reference transport coefficient obtained from experimental data, thereby canceling the exponential prefactor and leaving a compensated transport coefficient. We have demonstrated the validity and self-consistency of the CAF in a variety of organic liquids and their electrolytes over a wide range of salt concentrations (including ionic liquids!). We also developed a molecular-level picture of mass and charge transport in a polar liquid by modifying transition state theory and explicitly accounting for the role of the dipole polarization energy.