N-Doped Hollow Carbon Spheres Decorated with NiCo Alloy Nanoparticles for High-Performance Supercapacitors
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Nitrogen-doped hollow carbon spheres (NHCSs) decorated with NiCo alloy nanoparticles (NPs) were prepared and examined for their prospective role as high-performance electrode materials. The NiCo@NHCSs-23, composed of NHCSs with 23 wt% of NiCo alloy NPs, exhibited a specific capacitance (Csp) of 536 F g–1 when tested in a 6 M KOH solution at a current density of 1 A g–1. This high Csp is attributed to the synergistic effect of the faradaic charge storage provided by NiCo alloy NPs and the N-doped hollow carbon structure. Symmetric supercapacitor (SSC) devices were assembled using two NiCo@NHCS-23 electrodes and a 0.5 M Et4NBF4/PC electrolyte. The resulting SSC device operated within a potential window of 3.5 V and exhibited an energy density of 16.1 Wh kg-1 at the power density of 250 W kg-1. Notably, the SSC device demonstrated impressive cycling stability, maintaining 90.9% of capacitance and 100 % Coulombic efficiency after 5,000 cycles.