Carbon-based hierarchical mesoporous polyaniline/montmorillonite nanocomposites for high energy density supercapacitors

Developing high-performance energy storage technologies for the efficient use of portable electronic devices demands exploring new electrode materials. Conducting polymers are widely used in supercapacitors, in spite of their poor cyclic stability. The cyclic stability along with the energy storage ability can be enhanced with the addition of suitable nanofillers. Herein, we present the development of ternary nanocomposites of polyaniline (PANI), carbon black (CB), and montmorillonite (MMT) with varying compositions of the constituting components. The in-situ polymerization of PANI produces an evenly mixed nanocomposite. The detailed morphological analysis shows that the growth of PANI chains happens in the interlayer space of MMT, producing a hierarchical structure. Among all the composites, PANI/CB/MMT (16:1:1) shows the highest specific capacitance with remarkable cyclic stability. The fabricated symmetric supercapacitor based on PANI/CB/MMT (16:1:1) nanocomposite has further been examined in aqueous and gel (PVA/H2SO4) electrolytes, where the performance in the latter is higher than the former. The device produces an energy density of 107.2 Wh/kg and a power density of 2000 W/kg, at a current density of 1 A/g in gel electrolyte. Moreover, the device exhibits capacitance retention of ~98% after 6000 cycles at 5 A/g current density. The combined effects of enhanced electroactive sites, improved surface area, mesoporous structure, and low internal resistance provided by the synergistic effect of all the three components account for the increased performance of electrode material. An assembly of two such supercapacitors glows a red LED for ~6 min with a charging time of ~1 min.