Bamboo-Based Carbon Fiber/Carbon Nanosheet Composite Flexible Supercapacitor

The primary factors affecting the performance of supercapacitors are ion diffusion, storage, and electron conduction. A unique composite structure combining elongated carbon fibers and void-filling carbon nanosheets can simultaneously enhance ion diffusion, storage, and charge conduction. Herein, bamboo fibers treated with delignification are used as raw materials. Through a simple chemical delignification process, followed by compression into sheets and carbonization, elongated carbon fiber/carbon nanosheet composite structures are prepared. Supercapacitors made with symmetric electrodes from these bamboo-based composite materials exhibit a specific capacitance of 97.2 F g⁻¹ at a current density of 0.25 A g⁻¹. The bamboo-based composite sheets demonstrate excellent flexibility and conductivity due to the stacking of carbon fibers and carbon nanosheets, forming abundant layered voids and a 3D network structure. This layered 3D network structure endows the PVA/H₃PO₄ gel electrolyte with excellent permeability. The bamboo-based carbon fiber/carbon nanosheet composite interdigitated flexible solid-state supercapacitor achieves an areal capacitance of 10.59 mF cm⁻² at a current density of 5 μA cm⁻² and retains 0.99 mF cm⁻² even at 200 μA cm⁻². After undergoing various folding angles and 200 folds, the CV curves of the interdigitated flexible solid-state supercapacitor show minimal changes in shape and enclosed area, demonstrating excellent flexibility and folding durability.