High-performance hybrid supercapacitors based on cobalt sulfide and iron sulfide nanoparticles supported by hollow nitrogen-sulfur co-doped carbon spheres

Hybrid supercapacitor performance is predominantly governed by the electrochemical characteristics of their cathode and anode materials. Nevertheless, the coordinated construction of high-performance cathode and anode materials still faces challenges. In this study, sulfur-vacancy-rich CoS (V-CoS) nanoparticles were uniformly anchored onto the surface of hollow nitrogen-sulfur co-doped carbon (HNSC) spheres via a sodium borohydride-mediated chemical reduction strategy. The hollow porous architecture of HNSC and the introduction of sulfur vacancies synergistically enhance the electrochemical properties of CoS. The V-CoS/HNSC composite achieves a high specific capacity of 537.8 C g−1 at 1 A g−1 and maintains 96.3% of its capacity after 10000 cycles at 15 A g−1, showcasing excellent cycling stability. Subsequently, Fe3S4/FeS2 nanoparticles were uniformly grown on HNSC through a one-step solvothermal process. The specific capacitance of Fe3S4/FeS2/HNSC reaches 443.2 F g−1 at 1 A g−1 and retains 98.9% of its initial capacitance after 10000 cycles at 15 A g−1. Notably, the hybrid supercapacitor constructed with V-CoS/HNSC as the cathode and Fe3S4/FeS2/HNSC as the anode provides a high energy density of 78.4 Wh kg−1 (950.3 W kg−1). After 10000 charge-discharge cycles at 10 A g−1, the specific capacitance decay rate is merely 8.8%. These results highlight the significant potential of vacancy regulation and composite structure optimization in enhancing the energy storage performance of hybrid supercapacitors.