MXene/Polymer Hybrid Materials for Flexible AC-Filtering Electrochemical Capacitors

Energy storage devices are limited by the trade-off between the transport properties and charge storage ability of materials. Electrolytic capacitors are kinetically fast, operating at kilohertz frequency, but limited by low capacitance. Electrochemical capacitors (ECs) provide high capacitance, yet their sluggish kinetics limit frequency response to a few hertz. Here, we devise strongly interacting, porous MXene/conducting polymer hybrids for large-scale flexible alternating current filtering symmetric ECs with high areal and volumetric capacitances of 0.56 mF cm−2 and 24.2 F cm−3 at 120 Hz, respectively. The high capacitance was maintained up to 1,000 V s−1 and originates from synergy of MXene/polymer hybrids. The operation of tandem ECs that filter a pulsating voltage from 60 to 10,000 Hz is demonstrated with device flexibility and durability over 30,000 cycles. These MXene hybrid-based ECs are expected to bridge the performance gap between high capacitance and the high-frequency response toward the form-factor-free miniature and scalable devices.