The development of advanced electrochemical devices for energy conversion and storage requires fine-tuning of electrode reactions, which can be accomplished by altering the electrode/solution interface structure. Particularly, in the case of an alkali-salt electrolyte, the electric double-layer (EDL) composition can be managed by introducing organic cations (e.g., room temperature ionic liquid cations) that may possess polar fragments. To explore this approach, we develop a theoretical model predicting the efficient replacement of simple (alkali) cations with dipolar (organic) ones within the EDL. For the typical values of the molecular dipole moment (2–4 D), the effect manifests itself at the surface charge densities higher than 30 μC/cm2. We show that the predicted behavior of the system is in qualitative agreement with the molecular dynamics simulation results.
