Dual ligand (2MI/BI) promoting graphitic ordering and nitrogen enrichment in Fe-activated carbon nanofibers for freestanding flexible supercapacitors

초록

Flexible freestanding supercapacitors are essential for the development of energy-storage systems for use in portable, integrated, and wearable electronic devices. This study introduces a dual-ligand coordination method that utilizes 2-methylimidazole (2MI) and benzimidazole (BI) to produce nitrogen-doped activated carbon nanofibers (N-acCNFs) via electrospinning and carbonization. The use of 2MI and BI in the electrospinning precursor solution contributes to nitrogen enrichment and leads to the formation of dense, conductive carbon frameworks after carbonization. The N-acCNF electrodes are flexible and freestanding. The optimal electrode exhibits an areal capacitance of 730 mF & sdot;cm-2 at a current density of 1 mA & sdot;cm-2, along with a high rate retention of 63.4% at a current density of 25 mA & sdot;cm-2. The supercapacitor retains 93% of its initial capacitance after 10,000 galvanostatic charge-discharge cycles, and its cyclic voltammetry curves changed negligibly over 500 bending cycles, confirming its excellent electrochemical and mechanical stability. The supercapacitors effectively powered an 8 & times; 8 MAX7219 light-emitting-diode matrix when arranged in pouch-like assemblies and connected in series, demonstrating their use in display applications. Consequently, the developed freestanding fiber electrodes prepared by dual-ligand coordination through a simple multisyringe electrospinning process demonstrated excellent charge-storage capacities and rapid electron transport, and outperformed single-ligand-based electrodes.

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