Polyacrylonitrile-grafted lignin copolymer derived carbon nanofibers as a flexible electrode for high-performance capacitive-energy storage

Fabrication of flexible, low-cost, lightweight supercapacitors is in great demand for flexible electronics used in various applications. In this work, highly flexible carbon nanofibers (CNFs) were prepared using polyacrylonitrile grafted lignin (PAN-g-lignin) copolymers by electrospinning and consecutive stabilization/carbonization. The as-prepared PAN-g-lignin copolymer-derived CNFs were characterized by spectroscopy (FT-IR, NMR, FE-SEM, XRD), TGA-DSC, electrical conductivity, bending tests, and contact angles. The PAN-g-lignin-derived CNFs showed high carbon content, a uniform fiber structure, excellent flexibility for 5000 cycles at a bending radius of 10 mm, and remarkable retention (∼99.9%). A fabricated solid-state symmetric supercapacitor (SSC) device based on flexible CNFs possessed a high specific capacitance of 93.8 F g⁻¹ at 1 A g⁻¹ and excellent cyclic stability with 92% capacitance retention after 10 000 charge-discharge cycles. This fabricated SSC device delivered a high energy density of 33 W h kg⁻¹ at a power density of 800 W kg⁻¹, thereby demonstrating potential use for high-performance flexible energy-storage devices.