(524h) Dynamic Relaxations in the Electric Double Layers Comprised of Room Temperature Ionic Liquids

One of the key requirements for the electricity based energy storage devices is the ability to of fast charging/discharging to deliver more power. Understanding the mechanisms of electric double layer (EDL) formation at a molecular level is very important from both theoretical and application points of view as it could predict the kinetics of the non-Faradic processes and the internal resistance to the charge/discharge processes in supercapacitors. A systematic study of the EDL response to perturbations in the applied electrode potential for room temperature ionic liquid-based electrolytes at variety fo electrode surfaces will be presented. Under strong electric potential gradients generated in nanometer-scale EDLs investigated here, the charging/discharging processes was found to be a two-step process: i) the fast process consisting in a dipolar rearrangement of the ions near the electrode surface with co-ions quickly expelled into the outer layer and ii) a slow process that involves the ion diffusion through the entire cell in order to establish the ionic mass balance. The analysis of electrode charge fluctuations, electrolyte ordering near the surface and the total charge dependence as a function of time provided atomistic insight into mechanisms of formation of the electric double layer. We will also discuss our observations regarding the EDL response to oscillatory perturbations in electrode potential that emulate the cyclic voltammetry and impedance spectroscopy measurements. Finally, the frequency dependent dielectric response of the electrolyte within EDL will be correlated with predicted capacitance and discussed in light of available experimental data.