Unidirectional growth of polyaniline on 3D CoO nanowires for aqueous asymmetric supercapacitors

Metal oxide-based binary nanohybrids are a new class of binder-free supercapacitor electrodes. This paper reports the enhanced electrochemical performance of polyaniline (PANI)/CoO nanowires grown on Ni foam for use in aqueous asymmetric supercapacitors (SCs). Several synthetic parameters were optimized for the unidirectional growth of PANI on CoO nanowires. The rationally designed core-shell structured electrode exhibited a high specific capacity of 1113C g−1 (specific capacitance of 2473 F g−1) at a current density of 3 A g−1 and good cycling stability of 86.3 % over 10,000 charge/discharge cycles in a 1 M KOH electrolyte through a substantial synergistic contribution from each component. In addition, an aqueous asymmetric supercapacitor based on these PANI/CoO nanowire arrays exhibited a high specific energy of 35.8 Wh kg−1 and high cycling stability (89.1 % after 5000 cycles). Two aqueous asymmetric supercapacitors connected in series could light up 19 red light-emitting diodes (LEDs). Therefore, this electrode can be considered a superior candidate for the next-generation SC electrodes.