Facile synthesis of flexible electrode based on cotton/polypyrrole/multi-walled carbon nanotube composite for supercapacitors

Flexible electrodes made of cotton textile, polypyrrole (PPy) and multi-walled carbon nanotubes (MWCNT) composites were synthesized via a facile in situ chemical deposition method. This method involves a series of successive steps by immersing the cotton fabric in various MWCNT suspensions; adding monomers and p-toluene sulfonic acid (TsOH) as dopant under ultrasonic condition; and then initiating the polymerization by drop-in the oxidant. The fabricated electrodes exhibited a specific capacitance of 597 F g⁻¹ with good cycle stability (maintaining 96.8% after 1000 cycles). Symmetric all-solid-state supercapacitors based on cotton/PPy/MWCNT electrodes and poly(vinyl alcohol) (PVA)/H₃PO₄ gel electrolytes were fabricated and tested. The electrochemical measurements showed that assembled supercapacitors had a specific capacitance of 206.8 F g⁻¹ at a current density of 1 mA cm⁻². The supercapacitors were flexible enough to bend and twist with constant capacitance performance and exhibit 72% capacitance retention after 400 charge–discharge cycles.