ABSTRACT Achieving both high energy storage and superior rate capability in MXene‐based aqueous supercapacitors remains challenging. While Ti 3 C 2 T x ‐MXene demonstrates exceptional capacitance in H 2 SO 4 , its energy storage is limited by a narrow voltage window (1 V), but compromise specific capacitance and rate performance. To overcome this trade‐off, we develop an ultrafast microwave‐assisted acid etching strategy that produces holey‐crumpled MXene dispersions from pristine MXene within minutes. These dispersions are assembled into hierarchically porous MXene hydrogel‐electrodes through controlled vacuum filtration in a remarkably short time. In an engineered electrolyte containing LiCl and AlCl 3 , the resulting MXene electrodes exhibit superb pseudocapacitance, delivering a specific capacitance of 248.7 F g −1 at 10 mV s −1 and excellent capacitance retention of 60.7% at 2000 mV s −1 within a wide potential window of 1.3 V. This impressive supercapacitor performance stems from multi‐scale porosity that enhances electrolyte infiltration and ion transport, combined with mixed‐ion charge storage in LiCl/AlCl 3 electrolyte, where protons and mixed cations synergistically balance pseudocapacitance and rate capability. This work establishes the fastest route to holey MXene dispersions and showcases how structural hierarchy and mixed‐ion electrolytes collectively deliver high capacitance and rate performance in MXene supercapacitors.
Sikdar et al. (Sun,) studied this question.