High-performance supercapacitor based on a ternary nanocomposites of NiO, polyaniline, and Ni/NiO-decorated MWCNTs

Although high theoretical capacitance, low cost, and superior cycling reversibility make NiO a promising material for preparing supercapacitors, poor conductivity and ionic transport have limited its applicability. To overcome these drawbacks, in this study we prepared ternary composites from porous NiO nanosheets, polyaniline:poly(sodium 4-styrenesulfonate) (PANI:PSS), and Ni/NiO-decorated multiwalled carbon nanotubes (MWCNTs). Using a spray-drying technique, the conductive PANI:PSS was bound tightly to the porous NiO nanosheets to form PANI:PSS/NiO (P-NiO) microspheres. Here, the PANI:PSS infiltrated the nanopores of NiO and modified the NiO surface, thereby decreasing the internal resistance and avoiding restacking of the NiO nanosheets. Moreover, we synthesized MWCNTs decorated with Ni/NiO dual-phase nanoparticles; here, the deposition of the Ni/NiO nanoparticles improved both the electrical conductivity and capacitive behavior of the MWCNTs. As a result, the modified MWCNTs (m-MWCNTs) functioned as a novel additive that lowered the external resistance among the P-NiO microspheres. An asymmetric supercapacitor employing the designed ternary system and active carbon as electrodes achieved a remarkable specific capacitance of 105.6 F/g at 0.5 A/g, a maximum energy density of 33 W h/kg, and superior cycling stability.