NiCo 2 S 4 /MoS 2 Nanocomposites for Long-Life High-Performance Hybrid Supercapacitors.

Metal sulfides (MS) and mixed metal sulfides (MTMS) have been considered potential candidates over their metal oxide/mixed metal oxide counterparts in recent years. Herein, one MTMS, i.e., NiCo 2 S 4 , was combined with 2D MS MoS 2 through a single-step solvothermal process with different morphologies (sheet-like and rod-like) for supercapacitor applications. The resulting electrode exhibited excellent coulombic efficiency, high specific capacitance, superior energy density, and, most importantly, ultra-high cycling stability. In particular, the electrode delivered a capacitance of 2594 F g -1 at 0.8 A g -1 after 45,000 charge/discharge cycles with a remarkable stability of 192%. Moreover, the corresponding hybrid supercapacitor device displayed an impressive coulombic efficiency of 123% after 20,000 cycles and 118% after 45,000 cycles. In addition, the device also exhibited a decent energy density of 31.9 Wh kg -1 and good cycling stability of 102% over 15,000 cycles.