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 Ti3C2Tx 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 H2SO4 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 mu Wh cm-2 was recorded for a power density value of 855.5 mu W.cm- 2 at an areal current value of 0.5 mA cm-2. At a high current density of 10 mA cm-2, the energy density remained high at 99.0 mu Wh cm-2 for a corresponding power density of 8.11 mW cm-2. The reported values rank among the highest obtained for carbon nanotubes-based wired-shaped super -capacitors and show the potential of this flexible wired-shaped hybrid energy storage unit as a wearable device.