Polyaniline/carbon nanotube core–shell hybrid and redox active electrolyte for high-performance flexible supercapacitor

Integrated polyaniline/carbon nanotubes (PANI/CNTs) hybrid with shell/core nanostructure is fabricated by chemical vapor deposition and electrochemical deposition for flexible supercapacitor (SC) application. CNTs with homogeneous worm-like morphology and high conductivity are used as a skeleton to support high electrochemical active PANI. The PANI/CNTs core–shell hybrid displays high specific capacitance of 823 F g^− 1 in 1 M H₂SO₄ electrolyte at 5.0 A g^− 1, the enhanced specific capacitance of 1128 F g^− 1 was obtained with 0.02 M Fe³⁺/Fe²⁺ as redox additive in the electrolyte. Additionally, flexible symmetric SC has been assembled using PVA/H₂SO₄/Fe³⁺/Fe²⁺ as redox active gel electrolyte. The flexible SC exhibits an improved energy density as high as 22.9 Wh kg^− 1 at a power density of 700.1 W kg^− 1 and affords the capacitance retention of 97% after 2000 charge–discharge cycles. Furthermore, the fabricated SC device shows good flexibility and the output potential or current can be improved by connected three SC into series or parallel type. These results provide the potential and effective approach to enhance the electrochemical performances of flexible SC.