Polypyrrole-derived N-doped CNT nanocomposites decorated with CoNi alloy nanoparticles for high-performance supercapacitor electrodes

Polypyrrole-derived nitrogen-doped carbon nanotubes (NCNTs) decorated with CoNi alloy nanoparticles (NPs) (CoNi@NCNT) were prepared, and their electrochemical performance was evaluated for use as high-performance electrode materials. NCNT exhibit superior conductivity, electron transport pathway, and large surface area, and CoNi alloy NPs have good conductivity through multi-redox reactions and numerous active sites with electron transfer. The NCNT surface was decorated with different amounts of CoNi alloy using a simple wet impregnation method. The CoNi@NCNT nanocomposite loaded with 20 wt% CoNi alloy (CoNi@NCNT-20) exhibited the highest specific capacitance of 316 F g-1 at 1 A g-1 in 1 M aqueous H2SO4, which was two times higher than that of the pristine NCNT electrode. The synergistic effects of NCNT and CoNi alloy NPs were attributed to the fast ion transport caused by the excellent ion conduction between the NCNT and CoNi alloy during charge/discharge. Symmetrical supercapacitor (SSC) devices were assembled with a water-in-salt electrolyte. They showed a high potential of 2.4 V, a high specific energy density of 24.7 Wh kg -1, and a maximum power density of 5454.5 W kg -1. The SSC device exhibited excellent cycling stability of 94.6 % and could use high-energy storage to light up light-emitting diodes for practical examination.