Which is the main factor for improving the performance of the Graphene/MXene hybrid electrode: Ionic number, ionic distribution or ionic configuration?

Abstract

The Graphene/MXene hybrid, which has been proved by many studies for improving the re-stacking of MXene material, has been widely used as electrode material for supercapacitors. However, there are few reports about the energy storage mechanism of its electrical double layer (EDL), and especially the electrolyte is ionic liquids (ILs) in the electrochemical energy storage system. In this work, the molecular dynamics (MD) simulation was used to study the energy storage performance of three different types of electrodes using imidazolium-based ILs as electrolyte. It is found that compared with MXene material electrode, when the Graphene/MXene composite material is used as the cathode, the energy of the system increase after charging. Moreover, it is interesting to find that the improvement of the energy storage effect does not come from the change of the number of ions between the plates, but from the distribution variation of the imidazolium cations in two different configurations of ‘vertical’ and ‘parallel’ on the different electrode materials surface. At the same time, the dynamic distribution of anions will have a negative impact on the overall energy storage performance of the cathode, and the Graphene materials will aggravate this impact, but the increased layer distance after the Graphene and MXene composite can alleviate this impact. We believe the research is helpful to provide new insights into the design and selection of ionic liquid electrolyte and the application of electrode materials.