Study of the properties of nanoconfined EMIMBF4 using polarizable molecular dynamics

Abstract

We present a molecular dynamics study of the structure and dynamic behavior of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate under nanoconfinement using a polarizable force field. Two distinct geometries were explored: cylindrical confinement within carbon nanotubes and planar confinement between graphene-like nanoslits, covering a range of confinement sizes. Our results reveal that the geometry and curvature of the confining region play a fundamental role in determining ion layering, molecular orientation, and diffusion. In planar nanoslits, highly ordered interfacial structures form regardless of pore width, while in carbon nanotubes, curvature suppresses such ordering and enhances ionic mobility near the interfaces. For a specific nanotube size, an anomalous behavior emerges where the combination of confinement geometry and pore dimensions promotes the formation of stable ionic layers, which drastically reduce diffusivity. These findings provide insights into the design of electrochemical devices and the optimization of ion transport in confined ionic media.