Interfacial Layering and Screening Behavior of Glyme-Based Lithium Electrolytes

Understanding of electrical double layers is essential to all electrochemical devices, particularly at high charge carrier concentrations. Using a combined approach (surface force apparatus, zeta potential, infrared spectroscopy), we propose a model for the interfacial structure of triglyme electrolytes on muscovite mica. In contact with the pure triglyme, a brush-like polymeric structure grows on the mica surface. When lithium triflate is present in the triglyme, this structure is suppressed by anion adsorption and an extended double layer is formed. A surprising result of great fundamental significance is that the effective screening length measured by surface force apparatus at considerable lithium triflate concentrations (above 0.2 M) is substantially higher than expected from the Debye-Hückel theory. This suggests a high degree of complex salt association as a novel characteristic feature of salt-containing electrolytes.