PEDOT:PSS/Ketjenblack Holey Nanosheets with Ultrahigh Areal Capacitance for kHz AC Line‐Filtering Micro‐Supercapacitors

Supercapacitors, with their superior capacity and lower space occupancy, offer inherent advantages over aluminum electrolytic capacitors (AECs) in meeting the demands of miniaturization and planarization of devices. However, the capacitive advantage of supercapacitors is often compromised by the limited availability of electrode materials under high‐frequency alternating current conditions. The development of electrode materials that possess both high‐frequency response and high capacity is undoubtedly critical. Herein, PEDOT:PSS/Ketjenblack holey nanosheets (PKHNs) prepared by a solvent thermal method are successfully developed as the electrode material to ensure rapid ion transport and abundant charge storage on the accessible nanosheet surfaces. The micro‐supercapacitors exhibit a high‐frequency capacitance (3089 µF cm−2 at 120 Hz, with a phase angle of −81.9°), achieved through an innovative structural design utilizing PKHNs materials. These micro‐supercapacitors demonstrate excellent frequency response with efficient 120 Hz filtering and offer volumetric advantages over the state‐of‐the‐art commercial ones during low‐voltage operations, making them an ideal choice for the next‐generation miniaturized filter capacitors. The novel holey nanosheets are fabricated by assembling Ketjenblack nanoparticles and PEDOT:PSS nanofibrils. The unique nanostructure design and their excellent conductivity make them highly promising candidates for filter capacitors. The micro‐supercapacitors fabricated using these materials demonstrate superior AC line‐filtering and volumetric advantages compared to their commercial counterparts, thereby highlighting their potential for next‐generation miniaturized filter and energy electronics.