Constant potential molecular dynamics simulation of 1-Ethyl-3-Methylimidazolium Bis(trifluoromethanesulfonyl)imide in a supercapacitor

Abstract

Room temperature ionic liquid (RTIL), especially the imidazolium-based RTIL has been meticulously studied as promising electrolyte in energy storage devices. Due to the complexity of structural characteristics and dynamic properties, concrete understandings at a microscopic viewpoint when using RTIL as an electrolyte is essential. In this thesis, a classical molecular dynamic simulation of a supercapacitor model where 1-ethyl-3-methylimidzolium bis(trifluoromethylsulfonyl)imide ([C2mim][NtF2]) used as an electrolyte is conducted under voltage bias using a constant potential method. A distinct “checkered pattern” is observed by mass distribution and charge distribution after the equilibration and the pattern remains intact even at low voltage (0.0 V to 2.0 V). The pattern collapses after applying more than 3.0 V where the orientation analysis results of the [C2mim]+ cation also indicate a noticeable change after 3.0 V. The π-π stacking interaction between [C2mim]+ and the positively charged graphite electrode is clearly perceived. Furthermore, an exploratory analysis was conducted by using the principal component analysis (PCA) and k-mean clustering to characterize results from radial distribution function (RDF).