Scalable Electrostatic-Induced Control of Marangoni Deposition of Uniform 3D-Porous PEDOT Electrodes for Ultrafast AC-Line Filtering and High Areal/Volumetric Capacitance

With the miniaturization of integrated circuits driving increased demand for high-frequency alternating current (AC)-line filtering capacitors, portable electrochemical capacitors (ECs) must reconcile two persistent challenges: i) the inherent contradiction in synergistic enhancement between areal capacitance (C_A) and volumetric capacitance (C_V) at the condition of high frequency response, and ii) developing scalable fabrication methods. To address these issues, an electrostatic-induced Marangoni assembly process is introduced, which enables large-area, rapid deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) films with a uniform, 3D fibrous porous network. By pre-treating the PEDOT:poly(styrenesulfonate) (PSS) ink with a polar solvent and applying an electrostatic field, Marangoni flows align microdroplets into a continuously interconnected 3D architecture. This structure not only facilitates ultrafast ion transport but also provides abundant storage sites, yielding a sultaneous enhancement in C_A (1.72 mF cm⁻²) and C_V (13.2 F cm⁻³), as well as an exceptional phase angle of −82.9° at 120 Hz. These metrics surpass those of most reported carbon- and PEDOT-based filtering capacitors. Moreover, the method accommodates high-loading of pseudocapacitive materials, demonstrating its versatility for composite electrode engineering. Subsequent AC-line filtering tests confirm the practical applicability of these electrodes, offering a scalable route to miniaturized capacitors with synergistically optimized C_A and C_V.