A predictive dynamics simulation for the separation of lithium isotope through oriented defective graphene with electrochemical pumping

Abstract

The separation of lithium isotopes is crucial for the advancement of nuclear energy technology. Electrochemical pumping through two-dimensional membranes with a quantum sieving effect offers significant advantages over conventional methods such as chemical exchange and solvent extraction for separating lithium isotope ions. This study employs molecular dynamics simulations to investigate the permeation mechanism of lithium isotope ions through oriented defective graphene under an electric field and to determine the kinetic isotope effect (KIE). Simulation results reveal that, under an applied electric field, lithium ions gain sufficient kinetic energy to penetrate through electron cloud cavities formed by carbon rings with single or double vacancy defects, whereas pristine graphene effectively blocks their permeation. Further analyses of electron cloud density, transition state search, and energy barrier calculations confirm that lithium isotope ions can traverse the membrane at specific charge densities. The calculated single-stage separation factor for lithium isotopes using single-vacancy defective graphene reaches up to 1.22, which is significantly higher than that achieved by traditional separation methods. Moreover, the separation factor is demonstrated to be directly correlated with the electron cloud density of the carbon rings constituting the defect sites in graphene.