  We use molecular dynamics simulations to explore the impact of a non-ionic
solvent on the structural and capacitive properties of supercapacitors based on
an ionic liquid electrolyte and carbon electrodes. The study is focused on two
pure ionic liquids, namely 1-butyl-3-methylimidazolium hexafluorophosphate and
1-butyl-3-methylimidazolium tetrafluoroborate, and their 1.5 M solutions in
acetonitrile. The electrolytes, represented by coarse-grained models, are
enclosed between graphite electrodes. We employ a constant potential
methodology which allows us to gain insight into the influence of solvation on
the polarization of the electrodes as well as the structural and capacitive
properties of the electrolytes at the interface. We show that the interfacial
characteristics, different for two distinct pure ionic liquids, become very
similar upon mixing with acetonitrile.
