Application of external electric fields for Li+/Na+ ions separation in a graphene-based nano-channel: a computational study

Abstract

This study uses molecular dynamics simulations to investigate the efficient separation of lithium (Li⁺) and sodium (Na⁺) ions in graphene-based nano-channels under the influence of an electric field. The effect of nano-channel dimensions, including length and width, on the ion separation performance was investigated. Our results show that nano-channels with a length of 12 nm and a width of 1.5 nm exhibit optimal ion separation at the present electric field intensity of 4 mV/Å, with lithium ions preferentially accumulating in the designated storage compartments. This separation efficiency is primarily due to the mass-dependent electrophoretic mobility of the ions, with lithium ions migrating faster than sodium ions in the same electric field due to their lower mass and higher acceleration. In addition, the narrow channel width provides a more controlled laminar flow, minimizing turbulence and improving ion transport selectivity. This study also highlights the role of thermal effects, ion diffusion, and electrostatic interactions with the graphene surface in improving the separation process.