3D-printed sulfur-doped graphite-based carbon composite patterns for flexible and fast electrochemical capacitors

Flexible electrical double-layer capacitors (F-EDLCs) are promising as next-generation wearable energy storage devices owing to their high specific power density, safety, long cycle life, and eco-friendliness. However, F-EDLCs use in practical applications is challenging because they fail to achieve high flexibility and fast charge–discharge performance. To address this issue, previous studies of F-EDLCs have primarily modified carbonaceous materials, which are suitable active materials for flexible electrodes. In this study, we synthesized an optimized S-doped graphite-based carbon composite (2S-GCC) as the active material and fabricated net-patterned flexible electrodes via 3D-printing. The S-doped carbon lattice enabled fast electron transfer owing to efficient electron redistribution. Additionally, S-containing oxygen functional groups on the surfaces of 2S-GCC accelerated ion diffusion kinetics at the electrode–electrolyte interface owing to increased wettability. Furthermore, the 3D-printed net-patterned electrodes effectively alleviated localized mechanical stress that was applied to the electrode during repeated bending cycles. Thus, the synergistic effect of the chemical and morphological characteristics of 2S-GCC improved the charge transfer kinetics, and a 2S-GCC//2S-GCC full cell exhibited a fast rate capability (6.66 mF/cm² at 0.3 mA/cm²).