James J. Watkins

Supercapacitors demonstrate promising potential for flexible, multi‐functional energy storage devices; however, their widespread adoption is confronted by fabrication challenges. To access a combination of desirable device qualities such as flexibility, lightweight, structural stability, and enhanced electrochemical performance, carbon fiber (CF) can be utilized as a current collector, alongside graphene as an electrochemically active material. Yet achieving a cost‐effective, large‐scale graphene production, particularly on CF, remains challenging. Here, a rapid (<1 min) photothermal approach is developed for the large‐scale production of graphene directly onto CF, utilizing polyaniline (PANI) as a polymer precursor. The in situ electropolymerization of PANI on CF facilitates its rapid synthesis on large areas, followed by conversion into graphene networks, enabling the binder‐free fabrication of supercapacitor devices. These devices exhibit an areal capacitance of 180 mF cm −2 (at 2 mA cm −2 in 1 m H 2 SO 4 ), an order of magnitude higher than other fabric‐based devices. Moreover, the devised photothermal strategy allows for one‐step preparation of supercapacitor devices on areas exceeding 100 cm −2 , yielding an absolute areal capacitance of 4.5 F. The proportional increase in capacitance with device area facilitates scaling and indicates the commercial viability of this approach for low‐cost, energy‐efficient, and high‐throughput production of lightweight, high‐performance graphene‐based multi‐functional supercapacitor devices.