Design of thin-layer porous nickel cobalt sulfide for high-performance asymmetric supercapacitors

Bimetallic sulfides are promising energy materials due to the rich redox reactions. However, in most cases, NiCo2S4-based electrodes often suffer from the low specific capacitance and poor yield, this becomes the bottleneck of its large-scale application production. Here, we report a simple and efficient solvothermal-vulcanization method to fabricate large mass porous Nickel-Cobalt sulfide nanosheets for supercapacitor electrode materials. Prepared NiCo2S4 nanosheets combine the advantages of porous nanosheets (faster ion transport along the pores) and metal sulfides (TMSs) (higher theoretical capacitance), exhibit high specific capacitance performance (957 F g−1 at 1 A g−1) and good rate performance (503 F g−1 at 10 A g−1). Furthermore, the asymmetric supercapacitor (ASC) fabricated with NiCo2S4 NSs as the positive electrode and N-doped biomass-derived carbon(N-C) as the negative electrode also exhibits excellent electrochemical performance and high energy density(20.6 W h kg−1at 1.5 kW kg−1). One NiCo2S4 NSs//N-C devices can drive an electronic fan to rotate rapidly and two series devices can light a red LED continuously for more than 0.5 h. These results indicate the great advantages and potential of NiCo2S4 nanomaterials in the development of high-performance supercapacitor electrode materials.