Hierarchical PANI-Modified Ni–Co Sulfides/Oxide Nanostructures on Nickel Foam as Binder-Free Electrodes for High-Performance Asymmetric Supercapacitors

Supercapacitors' high-power density and quick charge–discharge cycles make them viable energy storage technologies. Transition metal sulfides have gained attention as electrode materials owing to their rich redox activity, low cost, and favorable electrochemical characteristics. In this study, a binder-free, vertically aligned polyaniline-modified Ni 3 S 2 –NiCo 2 S 4 –NiCo 2 O 4 (P-NCSO) nanocomposite was directly produced using a simple hydrothermal technique on nickel foam. The hierarchical architecture enhances ion transport, increases the active surface area, and improves electronic conductivity. The P-NCSO electrode exhibits a high specific capacitance of 2819 F g –1 at 1 A g –1 and retains 97.5% of its capacity after 7500 cycles. An assembled asymmetric supercapacitor (ASC) achieves 156.6 F g –1 at 1 A g –1, with a power density of 799.9 W kg –1 and an energy density of 55.6 Wh kg – 1 . The device maintains 95.2% capacitance retention and 98.9% Coulombic efficiency over 7000 cycles. These results highlight the potential of hierarchical P-NCSO architectures for high-performance supercapacitor applications.