Smart in situ construction of NiS/MoS2 composite nanosheets with ultrahigh specific capacity for high-performance asymmetric supercapacitor

NiS/MoS 2 composite nanosheets were designed and prepared via facile ion-exchange, freeze-drying, and Ostwald ripening processes. MoS 2 nanosheets served as backbones to absorb Ni 2+ ions and form NiS nanosheets. The electrode based on the NiS/MoS 2 composite nanosheets exhibited an ultrahigh specific capacity of 343.5 mA h g −1  at 9 A g −1 , which was superior to that of as-prepared MoS 2 nanosheets (125.8 mA h g −1 ) and Ni(OH) 2 nanosheets (148.9 mA h g −1 ). In addition, NiS/MoS 2 composite nanosheets presented an enhanced rate performance and good life cycle due to their hierarchical structure, high surface area with numerous active sites, and synergistic performance. A NiS/MoS 2 //AC asymmetric supercapacitor device operated in a large potential window (0–1.5 V) delivered a high capacitance of 48.4 F g −1  at 0.1 A g −1 , an excellent energy density of 15.1 Wh kg −1 and a very high power density of 2.25 kW kg −1 . This smart in situ construction process opens a new route to synthesize binary metal sulfides for high-performance energy storage devices.