NiCoSnanosheets decorated on nitrogen-doped hollow carbon nanospheres as advanced electrodes for high-performance asymmetric supercapacitors.

Taking advantage of both Faradaic and carbonaceous materials is an efficient way to synthesize composite electrodes with enhanced performance for supercapacitors. In this study, NiCoSnanoflakes were grown on the surface of nitrogen-doped hollow carbon nanospheres (NHCSs), forming a NiCoS/NHCS composite with a core-shell structure. This three-dimensionally confined growth of NiCoScan effectively inhibit its aggregation and facilitate mass transport and charge transfer. Accordingly, the NiCoS/NHCS composite exhibited high cycling stability with only 9.2% capacitance fading after 10 000 cycles, outstanding specific capacitance of 902 F gat 1 A g, and it retained 90.6% of the capacitance at 20 A g. Moreover, an asymmetric supercapacitor composed of NiCoS/NHCS and activated carbon electrodes delivered remarkable energy density (31.25 Wh kgat 750 W kg), excellent power density (15003 W kgat 21.88 Wh kg), and satisfactory cycling stability (13.4% capacitance fading after 5000 cycles). The outstanding overall performance is attributed to the synergistic effect of the NiCoSshell and NHSC core, which endows the composite with a stable structure, high electrical conductivity, abundant active reaction sites, and short ion-transport pathways. The synthesized NiCoS/NHCS composite is a competitive candidate for the electrodes of high-performance supercapacitors.