Effect of ionic liquid saturation on electrode interface behavior and capacitance

This study employs molecular dynamics simulations to investigate four representative ionic liquids ([Bmim]Cl, [Bpy]Cl, [Bpip]Cl, [Bpyr]Cl) in conjunction with a PTCDA-based negative electrode interface. It systematically explores the impact of ion structure (saturated/unsaturated heterocycles) on interfacial adsorption behavior, electric double-layer capacitance, and energy storage efficiency. We conducted multidimensional analyses, including number density distribution, mean square displacement (MSD), radial distribution function (RDF), and conformational distribution, to explore the interfacial behavior in detail. Due to it-it interaction and strong electrostatic adsorption, unsaturated cations form a compact and ordered double layer structure at the interface, and the capacitance value is significantly higher than that of saturated cations. Compared to their unsaturated counterparts, saturated cations demonstrate greater diffusion rates, which may contribute to improved rate performance in energy storage devices. This research offers theoretical guidance for tailoring ionic liquid molecules and optimizing supercapacitor interfaces.