Core–Shell Structured Carbon Nanofiber-Based Electrodes for High-Performance Supercapacitors

The combination of multiple electrode materials and their reasonable structural design are conducive to the preparation of composite electrodes with excellent performance. In this study, based on carbon nanofibers grown with Ni(OH)(2) and NiO (CHO) prepared by electrospinning, hydrothermal growth, and low-temperature carbonization, five transition metal sulfides (MnS, CoS, FeS, CuS, and NiS) were hydrothermally grown on their surfaces, exhibiting that CHO/NiS had the optimal electrochemical properties. Subsequently, the effect of hydrothermal growth time on CHO/NiS revealed that the electrochemical performance of CHO/NiS-3h was optimal, with a specific capacitance of up to 1717 F g(−1) (1 A g(−1)), due to its multistage core–shell structure. Moreover, the diffusion-controlled process of CHO/NiS-3h dominated its charge energy storage mechanism. Finally, the asymmetric supercapacitor assembled with CHO/NiS-3h as the positive electrode demonstrated an energy density of 27.76 Wh kg(−1) at a maximum power density of 4000 W kg(−1), and it still maintained a power density of 800 W kg(−1) at a maximum energy density of 37.97 Wh kg(−1), exhibiting the potential application of multistage core–shell composite materials in high-performance supercapacitors.