High-performance novel asymmetric MXene@CNT//N-doped CNT flexible hybrid device with large working voltage for energy storage

We developed a novel fiber-shaped supercapacitor based on a hybrid MXene@CNT//N-doped CNT device. In particular, for the first time, electrophoretically deposited TiCT MXenes on carbon nanotube yarns and microwave-assisted nitrogen-doped carbon nanotube yarns are proposed as negative and positive electrodes, respectively. Short-circuit encountered during cell assembly was prevented entirely by coating a reproducible polyvinylidene difluoride (PVDF) membrane directly on the electrodes. Based on the developed electrodes, the assembled cell exhibited a large operating voltage window of up to 2.0 V in a diluted 0.5 M HSO liquid electrolyte. The device displayed excellent stability over 5000 cycles with a Coulombic efficiency of nearly 100 %. The device withstood a floating test for 70 h with approximately 100 % capacity retention and exhibited excellent resistance to mechanical stress. Areal energy density as high as 298.5 ?Wh cm was recorded for a power density value of 855.5 ?W.cm at an areal current value of 0.5 mA cm. At a high current density of 10 mA cm, the energy density remained high at 99.0 ?Wh cm for a corresponding power density of 8.11 mW cm. The reported values rank among the highest obtained for carbon nanotubes-based wired-shaped supercapacitors and show the potential of this flexible wired-shaped hybrid energy storage unit as a wearable device.