Effects of functional groups and anion size on the charging mechanisms in layered electrode materials

Abstract

Highlights : We have conducted molecular simulations on 20 model supercapacitors systems based on graphene or MXene electrodes, with different functional groups, and 5 neat ionic liquids, with different anions.When charging negatively, the electrodes expand and no major dependence on the anion type is observed. When charging positively, the volume changes are more complex.Volume changes are generally very well correlated with the quantities of adsorbed ions, except for the largest anions for which ion reorientations affect the interlayer spacing.We demonstrate that the charging mechanisms are largely correlated with the anion sizes and the surface charge of the electrode material in the uncharged state.