Humidity Exposure Enhances Microscopic Mobility in a Room-Temperature Ionic Liquid in MXene

Present and future electrochemical devices employing advanced electrode and electrolyte materials are expected to operate in diverse environments, where they are exposed to variable conditions, such as changing humidity levels. Such conditions can possibly alter the microscopic mechanisms that influence the electrochemical performance. Here, using quasi-elastic neutron scattering and molecular dynamics simulations, we investigate the influence of humidity exposure on a room-temperature ionic liquid, [EMIm⁺][Tf₂N^-], in Ti₃C₂T_x MXene. Absorbed water enhances the microscopic mobility of confined [EMIm⁺][Tf₂N^-], even though the ionic liquid itself is not very hygroscopic. The absorbed water molecules predominantly reside on the termination groups of the more hydrophilic MXene layers, thereby displacing the ions from the surface and facilitating their motions in the MXene matrix.