Impact of Humidity on the Mobility of an Ionic Liquid Confined in Ti₃C₂T_X MXene

MXenes are two-dimensional materials with a potential in energy storage applications, especially as electrode materials in supercapacitors. MXenes provide high volumetric capacitance, but still have some limitations affecting their power capabilities. On the other hand, high energy and power density can be achieved using room temperature ionic liquids (RTILs) as an electrolyte that withstands a high operational potential window. Here, as an effort to overcome the high voltage limitation, and to provide a guidance for the development of most robust energy storage systems in the future, we have investigated the microscopic dynamics of a RTIL, [EMIm⁺][Tf₂N^-], confined in a Ti₃C₂T_X MXene. We have found that the ionic liquid was confined between the stacks rather than in between the layers of the MXene, thus showing a diffusion coefficient at about a half of the bulk value. This result is consistent with the unchanged c-lattice parameter revealed by X-ray diffraction measurement after the ionic liquid intercalation. An increase in the overall cation diffusivity after water vapor exposure, as revelaed from quasi-elastic neutron scattering (QENS) and molecular dynamics simulations, will be presented.