Swelling-reconstructed chitosan-viscose nonwoven fabric for high-performance quasi-solid-state supercapacitors

Fabrics are often used as freestanding substrates for energy storage devices owing to their hierarchical porous structure and excellent mechanical flexibility. However, it is still a challenge to achieve a high loading mass of electroactive materials for outstanding electrochemical performance. In this work, with the help of high swelling property of chitosan, the chitosan-viscose nonwoven fabric (CVF) is successfully reconstructed to expand its specific surface area for flexible conductive substrates in the supercapacitors. Then, multi-walled carbon nanotubes (MWCNTs) are coated on the surface of crosslinked chitosan-viscose nonwoven fabric (c-CVF) to form the conductive framework. Subsequently, polypyrrole (PPy) is deposited by in-situ interfacial polymerization on the above conductive MWCNT/c-CVF substrate. The optimized PPy/MWCNT/c-CVF composite electrode shows not only a high electrical conductivity of 285.9 ± 1.2 S·cm^-1, but also a prominent specific capacitance of 10112.9 mF·cm^-2 at 2 mA·cm^-2. Moreover, the prepared composite electrode also exhibits a high flexibility and good rate capability, in which the 70.3% capacitance is retained when the current density increases from 2 mA·cm^-2 to 10 mA·cm^-2. Besides, the quasi-solid-state symmetric supercapacitor, being assembled with the optimized composite fabric electrodes, produces the maximum areal specific capacitance of 1748.0 mF·cm^-2 at 2 mA·cm^-2 and the outstanding energy density of 155.4 μWh·cm^-2 at a power density of 0.88 mW·cm^-2. This work provides an effective approach to reconstruct the blended nonwoven fabric structure for high-performance flexible conductive substrate in the supercapacitors.