Systematic design of MXene/thermoplastic polyurethane/carbon nanotube@polypyrrole fiber electrodes for efficient flexible fiber supercapacitors.

MXene exhibits exceptional electrical and electrochemical properties, and is regarded as a promising candidate for future wearable electronic products. However, achieving a balance between flexibility and capacitance performance in MXene-based fiber supercapacitors remains a challenge. Here, MXene/Thermoplastic polyurethane (TPU) composite fibers with good conductivity and tensile properties, were prepared by wet spinning method. A carbon nanotube (CNT) film with continuous network structure was introduced on the surface of MXene/TPU composite fiber as a conductive interfacial layer to deposit a uniform and dense polypyrrole (PPy) array controllably. This structure is beneficial for improving the utilization of PPy and can enhance the overall strength and flexibility of composite fibers. The MXene/TPU/CNT@PPy composite fiber electrode demonstrates promising electrochemical performance, with a specific capacitance of 579F/cm (at a current density of 1 A/cm). The assembled flexible fiber supercapacitor exhibits a power density of 499.8 mW/cm and a corresponding energy density of 16.3 mWh/cm (1 A/cm), suggesting potential applications in flexible and wearable energy storage devices and textiles.