Vertically Oriented MXene Bridging the Frequency Response and Capacity Density Gap for AC-Filtering Pseudocapacitors

Electrochemical capacitors (ECs) with high-rate characteristics demonstrate great promise for replacing bulky aluminum electrolytic capacitors with alternate current (AC)-filtering functions. Currently, the performance of AC-line filtering ECs is limited by the vast gap between the ionic transport kinetics and capacity density of electrode materials. Herein, vertically oriented MXene and reduced graphene oxide composite (VMG) electrodes are prepared by electrochemical co-deposition to bridge the performance gap for AC-line filtering ECs. Benefiting from the unique pseudocapacitive characteristic and vertically interconnected microstructure, the VMG-based EC exhibits an outstanding areal capacitance of 1.14 mF cm⁻² with a phase angle of −80° at 120 Hz. Moreover, by utilizing the advantages of MXene at negative potential, an asymmetric pseudocapacitor is constructed with an energy density up to 805 µF V² cm⁻² at 120 Hz, which can be further incorporated in portable and wearable devices with excellent environmental ripple filtering capability in diverse scenarios.