Flexible supercapacitors based on free-standing polyaniline/single-walled carbon nanotube films

Advances in supercapacitor performance are boosted both by material design helping to improve specific capacitance and by tailoring of device architecture, often addressing flexibility to enable rolling-up packaging to reach high nominal values. This keeps attention to flexible lightweight materials, such as single-walled carbon nanotubes (SWCNTs), and conducting polymers, such as polyaniline (PANI). In this work, we design and study unique “dead-weight” free supercapacitors based on PANI electrochemically deposited on free-standing SWCNT films. Depending on the carbon nanotube film characteristics, we adjusted polymer inclusion into the nanotube films and evaluated its structure by TEM, SEM, XPS and Raman spectroscopy. Electrochemical methods were used to investigate the relationship between the morphology of initial SWCNT films, deposited PANI, and the electrochemical properties of the composite materials, including specific gravimetric capacitance and self-discharge processes. We show that thin free-standing films of SWCNTs with deposited PANI are less prone to self-discharge due to higher resistance arising from the lower density of the nanotubes in the film. Yet, such films enable better and more uniform deposition allowing to reach the maximum gravimetric capacitance value of 541 F g⁻¹. This synergistic performance allows the creation of an electrode material for flexible ultra-light and powerful supercapacitors.