Title: Contribution of carbon mesopores towards the improved performance of ionic liquid-based EDLCs at different temperatures

Abstract

During the presentation an important role of mesopores investigated in electric double-layer capacitors (EDLCs) operating from 24°C down to−40°C by using carbons with hierarchical porosity will be discussed. Home-made carbons were prepared using different precursors as the carbon source, while a binary mixture of imidazolium-based fluorinated ionic liquids was used as a solvent-free electrolyte. It will be shown that short-range graphene layers produced with 8-nm silica nanoparticles lead to the creation of transport channels which better accommodate ions. We explain these findings per coulombic interactions among the ions and between the pore wall and the ionic species under confinement and electrochemical polarization conditions. Further, it will be shown that a microporous carbon performs better than hierarchical carbons at room temperature; however, owing to the large fraction of mesopores, the latter exhibit far higher capacitance down to−40°C. While the ordering of ions in confinement is more critical at room temperature and dictated by the micropores, low temperature performance of supercapacitors is determined by the mesopores that provide channels for facile ion movement and keep the bulk ionic liquid–like properties.