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 m2/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 sp2 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.