Molecular dynamics simulations of ionic liquids confined into MXenes

Two-dimensional (2D) transition metal carbides known as MXenes have been extensively investigated as electrode material of electrochemical devices , including supercapacitors . Here we present a detailed computational study of ionic liquids in contact with Ti 3 C 2 F 2 , both at planar surface and under confinement. The simulations employ an extension of the constant potential model (CPM χ ) that can properly deal with materials composed of chemical elements with different electronegativities . The average partial charges of MXene atoms calculated with CPM χ are in excellent agreement with the ones obtained by DFT calculations. The differential capacitance and the charging mechanisms are thoroughly analyzed for two ionic liquids with a common cation, [ EMIM ] [ BF 4 ] and [ EMIM ] [ NTf 2 ] . By varying the MXene interlayer dimension, the best performance in terms of charge storage is obtained in electrodes with 12.6 Å spacing, with outperformance of [ EMIM ] [ BF 4 ] -based cells.