N-Doped NiO@MXene/Carbon Nanofiber Composites for High-Performance Flexible Supercapacitor Electrodes

MXene-based materials have attracted particular research interest as innovative electrodes for energy storage systems. However, fabricating these electrodes poses a considerable challenge because of their low-rate performance and sluggish ion transport, which results from the self-restacking of MXene flakes. A promising strategy to overcome these hurdles and enhance performance involves creating MXene-integrated fiber electrodes and subsequently modifying their surfaces via nonthermal plasma. In this work, flexible nitrogen-doped NiO@Ti3C2Tx/CNF composite electrodes were prepared by using a needleless electrospinning technique, followed by nitrogen plasma treatment. N-doping by nonthermal plasma increases the pseudocapacitive contribution of the NiO@Ti3C2Tx/CNF and improves both surface wettability and cycling stability of the electrode. This distinctive architecture offers benefits, including an expanded surface area, great conductivity, and high-rate performance. The N-doped NiO@Ti3C2Tx/CNF electrode demonstrated a significant specific capacitance of 871 F g–1 at 1 A g–1 in a 3 M KOH electrolyte. Moreover, a novel asymmetric supercapacitor was established, utilizing N-doped NiO@Ti3C2Tx/CNF and activated carbon (AC) as positive and negative electrodes, respectively. The electrochemical performance indicated a high energy density of 63.5 Wh kg–1 at a power density of 750 W kg–1 with 92% capacitance retention after 5000 cycles for the N-doped NiO@Ti3C2Tx/CNF//AC ASC. This result opens up possibilities for the development of next-generation energy-storage systems.