The effect of pore size of the nanoporous activated carbon on the thermal behavior of confined 1–ethyl–3–methylimidazolium bis(trifluorosulfonyl)imide [EMIM TFSI

Abstract

We report the melting behavior of ionic liquid 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) confined in nanoporous carbons. The ionic liquids (ILs) are recently mentioned as promising substances in electrochemistry as electrolytes in supercapacitors. The investigation of melting behavior of applied ionic liquid is important for low temperature operation conditions for supercapacitors. In this work, we presented the experimental studies of the melting behavior of EMIM TFSI confined in carbon micropores of about 1.4 nm pore size and also carbon mesopores of pore size of 4.6 nm. The methods of Dielectric Relaxation Spectroscopy (DRS) and Differential Scanning Calorimetry (DSC) in wide temperature ranges were applied. To investigate structural properties of the systems, temperature-controlled Wide-angle X-ray scattering (WAXS) and Neutron Diffraction (ND) methods were adopted. The results obtained from DSC and DRS indicate that the melting temperature of EMIM TFSI confined in carbon nanopores decrease relative to the bulk ionic liquid. Analysis of the structures and dielectric relaxation processes of the EMIM TFSI below their pore melting point indicates the different structure and slower dynamic of EMIM TFSI confined in pores relative to the bulk.