Unzipped MWCNT/polypyrrole hybrid composites: a pathway to high-performance asymmetric supercapacitors†

Abstract

A novel method has been developed for the conversion of multi-walled carbon nanotubes (MWCNTs) into unzipped MWCNTs (UzMWCNT) using a modified Hummer's method followed by reduction. This technique allows for the controlled modification of MWCNTs in both transverse and longitudinal directions. The UzMWCNT exhibits unique structural characteristics that combine the properties of 1D nanotubes and graphene-like features. The UzMWCNT/PPy composite exhibited an impressive specific capacitance of 944 F g⁻¹ along with excellent cycling stability, retaining 92% of its capacitance after 5000 cycles. For the UzMWCNT/PPy//AC composite, the gravimetric capacitance decreased with increasing current density, from 400 F g⁻¹ at 1.0 A g⁻¹ to 162 F g⁻¹ at 2.5 A g⁻¹. Furthermore, the UzMWCNT/PPy//AC composite demonstrated outstanding long-term durability, retaining approximately 95% of its capacitance after 5000 cycles at a current density of 5 A g⁻¹, underscoring its excellent cycling stability. This research paves the way for the development of high-performance supercapacitor electrodes using hybrid materials derived from MWCNTs.