Flexible, Degradable, and Flame-Retardant CaAlg/CNT/PPy Composite Fiber Electrodes for High-Performance Fiber-Shaped Supercapacitors

With the growing emphasis on environmental consciousness and personal safety awareness, fiber electrodes featuring excellent environmental friendliness and safety performance are crucial for developing high-performance close-fitting wearable electronics. Herein, a flexible, degradable, and flame-retardant calcium alginate (CaAlg)/carbon nanotubes (CNTs)/polypyrrole (PPy) composite fiber electrode is developed for advanced fiber-shaped supercapacitors (FSSs). Benefiting from the intrinsic biodegradable and flame-retardant properties of CaAlg matrix, the composite fiber electrode exhibits controllable degradability and superior flame retardancy. Moreover, owing to the unique wrinkled PPy layer that synergistically improves both electrochemical and mechanical properties, the ternary CaAlg/CNT/PPy composite fiber electrode shows a remarkable areal capacitance of 1308 mF cm –2 at 2 mA cm –2 and an outstanding mechanical strength of 45 MPa. The as-fabricated FSS device delivers a high energy density of 10.9 μWh cm –2 , outperforming most state-of-the-art flexible FSSs, especially those based on biomass-derived fibers. These flexible composite fiber electrodes hold great promise for the development of high-performance, high-safety energy storage devices toward sustainable portable and wearable electronics.