Flexible Fiber Supercapacitor Using Biowaste‐Derived Porous Carbon

A flexible fiber supercapacitor (SC) was fabricated by using porous carbon as the electrode material and polyvinylalcohol–H 3 PO 4 as the gel‐polymer electrolyte. The porous carbon was derived from dead Ficus religiosa leaves through a single‐step carbonization method and characterized by using BET surface area and TEM analysis as well as XRD, Raman, and FTIR techniques. The fabricated fiber SC works up to 0.8 V and delivers a gravimetric (length) capacitance of 3.4 F g −1 (4.2 mF cm −1 ) at 1 mA. In addition, it exhibits a maximum gravimetric (length) energy density of 311 mWh kg −1 (37.3×10 −8  Wh cm −1 ) at a power density of 58 W kg −1 (70.3 μW cm −1 ) with a capacitance retention of 88 % over 4000 cycles.