MOLECULAR DYNAMICS SIMULATION OF BINARY MIXTURE OF IONIC LIQUIDS NEAR CARBON ELECTRODE: THE CAPACITIVE PERFORMANCE AND TEMPERATURE EFFECTS

摘要

The current utility of room temperature ionic liquids (RTILs) is restricted by the limited operating temperature range, which is mostly within 293-353 K. In order for supercapacitors to be used under severe cold weather conditions,ionic liquids with lower melting points are essential while retaining the capacitance. In this direction, binary mixture of RTILs exhibited reduced melting temperature than either of the neat RTILs and widened liquidus range, thus favoring the low-temperature application of RTILs. Hence, in this work, atomistic MD simulation was applied to model pure and mixed RTILs as electrolytes near onion-like carbon (OLC) and carbon nanotube (CNT) electrodes as a function of temperature. The ionic liquid electrolytes used in this study are [C3mpy][Tf2N], [C4mpip][Tf2N] and the equimolar mixture of these two ionic liquids. The aim of this work is to interpret how the binary electrolytes at varying temperatures influence the electrical double layer (EDL) microstructure and the capacitance of OLC-based supercapacitors. The results also demonstrate that binary RTILs electrolytes exhibit higher conductivity than either of the neat RTILs; that the C-V curve of binary mixture near OLC manifested the similar shape as those of neat RTILs and that the capacitance values increase as temperature increases; that the temperature dependence of capacitance is related to the EDL microstructure, mainly dominated by the EDL thickness.