Activated Carbon Nanofiber Sheets Derived from Electrospun Lignin: PVA Blend for Flexible Supercapacitors

Abstract

The present investigation reports the performance of ultra-flexible activated carbon nanofiber sheets (ACNF) as a flexible electrode for supercapacitors application. ACNF was fabricated by pre-carbonization at 600 °C and then by activation using potassium hydroxide (KOH) at 800 °C. These ACNF sheets prepared via the facile electrospinning technique possess the morphology of the nanofiber network with the diameter range (600-1400 nm) of the carbon. The findings demonstrate that the activation method not only enhances the sheet's surface area (806.9 m 2 /g) and total pore volume (0.519 cc/g) but also eliminates the lignin polymer's inherent sodium (Na) impurity through washing. This interconnected nanofiber sheet possesses high electrical conductivity of 8.40 S/cm. These sheets exhibit cloth-like flexibility with high electrical conductivity and porosity, making them suitable candidates for flexible electrodes. Raman spectroscopy was also carried out to get information about sp 2 carbon. Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS) were performed to understand the electrochemical performance of the sheets as electrodes. This ACNF sheet demonstrate a higher specific capacitance of 203.29 F/g at a current density of 1 A/g in a three-electrode configuration. Furthermore, a flexible supercapacitor device was fabricated using an ACNF sheet due to its high flexibility, stand-alone character, and excellent performance as an electrode. The device exhibits a high energy density of 65.52 Wh/kg and a power density of 1036.27 W/kg with high coulombic efficiency (99.6%) after 10,000 cycles. Also, the prepared device illuminated the seven-segment display in various bending conditions showing its flexibility.