Rapid Synthesis of Hierarchically Porous Hydrogel Frameworks Derived From Holey‐Crumpled MXene Dispersion for High‐Voltage Aqueous Supercapacitors

Achieving both high energy storage and superior rate capability in MXene-based aqueous supercapacitors remains challenging. While Ti₃C₂T_x-MXene demonstrates exceptional capacitance in H₂SO₄, its energy storage is limited by a narrow voltage window (<1 V). In contrast, neutral electrolytes enable a wider 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 AlCl₃, 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/AlCl₃ 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.