Scalable in-situ formation of amorphous NiCoSx nanosheets on porous carbon-based nanofibers for asymmetric supercapacitors

The delicate integration of carbonaceous scaffolds and transition metal sulfides (TMSs) has recently achieved a series of positive results in supercapacitors. However, these hybrids usually suffer from weak compatibility and combination at the heterogeneous interface, leading to the peeling of TMSs and capacity fading of electrodes during the long-term charge/discharge processes. Herein, a facile and scalable in-situ sulfidation technique is designed for the construction of stable supercapacitor electrodes, where porous NiCo/C nanofibers act as the core to support the shell materials of amorphous NiCoSx nanosheets, with the formation of well-defined NiCo/C@NiCoSx (CNCS) core-shell architectures. The mass loading and size of the outer NiCoSx nanosheets are heavily dependent on the carbonization temperature of the inner NiCo/C nanofibers, which can dramatically impact the electrochemical property of the hybrids. The optimized CNCS electrode exhibits an excellent specific capacity and a high rate capability. The assembled asymmetric supercapacitor presents a satisfactory energy density (38.73 W h kg−1) at 800 W kg−1 and a favorable stability with a high capacitance retention (93.1%) after 8000 cycles. This in-situ strategy to regulate the heterogeneous interface is promising for the development of stable TMS-based electrodes and supercapacitors.