A coupled conductor of ionic liquid with Ti3C2 MXene to improve electrochemical properties

Abstract

Ti₃C₂T_x MXene is regarded as a promising material in energy-related applications; however, the overscreening charge effect of the electric double layer on electrified interfaces, along with “inert” F terminations, limits the electrochemical operation efficiencies. Here, we developed a protocol to harvest a coupled conductor through confining in situ 1-ethyl-3-methylimidazolium ([Emim]⁺) ions into Ti₃C₂T_x interlayers. The ionic–electronic coupling does not require any external counterions, but activates terminal F and even sub-surface Ti, and endows the conductor with metal-like and ionophilic characteristics. Different from physically preintercalated or adsorbed ions, the resulting chemically confined [Emim]⁺ ions offer more accessible electroactive sites, faster electron transport in surface redox, and more efficient channels for ion transfer. Hence, the Ti₃C₂T_x electrodes present high gravimetric capacitance, rate performance and cycling stability. This work highlights the important roles of the coupling in the design and research of mixed ionic–electronic conductors with high electrochemical activity.