Polypyrrole-Decorated Hierarchical NiCo₂O₄ Nanoneedles/Carbon Fiber Papers for Flexible High-Performance Supercapacitor Applications

A novel polyprrole (PPy)-decorated hierarchical NiCo₂O₄ nanoneedles was grown on highly conductive carbon fiber paper (CFP) for high performance asymmetric supercapacitor applications. The PPy-decorated hierarchical NiCo₂O₄ nanoneedle on CFP (PPy-NiCo₂O₄@CPF) was grown by two steps. At first, NiCo₂O₄ nanoneedle was grown by hydrothermal process and followed by the deposition of PPy through electrochemical method. The fabricated PPy-NiCo₂O₄@CPF electrode displayed the higher electrochemical performance. The specific capacitance was ∼910 F g-1 at a current density of 1 A g⁻¹ and cyclic stability was ∼88% after 10,000 cycles. To explore real performance of the electrode, we have fabricated solid state asymmetric supercapacitor using PPy-NiCo₂O₄@CFP as positive and nitrogen doped reduced graphene oxide (N-rGO) as negative electrodes. The fabricated asymmetric device delivered a specific capacitance of 118.6 F g-1 at a current density of 1.0 A g⁻¹ with a maximum energy density of 40.81 Wh Kg⁻¹ (at a power density of 738.27 W Kg⁻¹) and maximum power density of 3746.77 W Kg⁻¹ (at an energy density of 13.53 Wh Kg⁻¹). The impressive results suggest that flexible PPy-NiCo₂O₄@CFPs can be a promising electrode material for supercapacitor applications.