MXene and Ionic Liquid based Electrode Materials for Supercapacitors

Abstract

MXenes are a new group of layered 2D materials that were discovered by Gogotsi et al. in 2011 and have gained lots of interest since. They have potential for many applications, showing excellent promise especially in electrical energy storage. They have mostly been studied for supercapacitors due to their 2D structure, good electrical conductivity, and hydrophilicity. Their capacitance values are already comparable with conventional carbon based supercapacitors, and as for that, MXenes have a possible role in future as an energy storage material once the performance reaches the required state in all the areas. Ionic liquids have played an important role in electrochemical applications owing to their relatively low toxicity, low vapor pressure and a high stability. Herein we have used an environmentally friendly ionic liquid choline bis(trifluoromethylsulfonyl)imide to intercalate between the 2D MXene (Ti3C2Tx), which led to interlayer expansion between the sheets. The electrochemical performance of these composite materials was studied for supercapacitor applications. The aim of this research was to enhance the electrochemical performance of Ti3C2Tx by using ionic liquid as an intercalant to increase the interlayer spacing. Ti3C2Tx was synthesized by etching aluminum from the corresponding MAX phase material (Ti3AlC2) by using LiF and HCl. The MXene – ionic liquid composite material was made by intercalating choline TFSI ionic liquid into the MXene powder in different ratios (2:1, 1:1, 1:2, 1:5 and 1:10). The composite materials were characterized using PXRD, UV-vis spectroscopy, TGA, FTIR and FESEM. Electrochemical performance was tested with cyclic voltammetry, galvanostatic charge – discharge and charge – discharge stability in H2SO4 electrolyte in a symmetric two electrode configuration. Intercalation of ionic liquid into Ti3C2Tx was successful for 2:1, 1:1 and 1:2 ratios as the interlayer spacing was increased. For 1:5 and 1:10 intercalation didn’t expand the sheets. As the capacitance values for the composites remained low, further studies should be made to study the effect of surface chemistry on the electrochemical performance of the composite materials.