Fabrication coralline Ni-Mo-O-S composites as advanced electrodes for high-performance asymmetric hybrid supercapacitors

In this work, the coralline nickel molybdenum oxide and sulfide (Ni-Mo-O-S) composites were successfully synthesized by two-step hydrothermal method. The coralline structure has large specific surface area and enriched porosity, which makes the composites have excellent electrical conductivity. Furthermore, the synergistic effect of Ni and Mo elements and the addition of S2− ions improved the electrical conductivity and electrochemical performance of Ni-Mo-O-S. The electrochemical performance of the prepared materials was evaluated in detail. Specifically, the Ni-Mo-O-S composites achieved a high specific capacity of 330.2 mA h/g (3714.4 F/g) at a current density of 1 A/g, even 317.5 mA h/g (3265.5 F/g) at 5 A/g, as well as showing good rate performance and improved cyclic stability (75% capacitance retention after 3000 cycles). The asymmetric supercapacitor device assembled from Ni-Mo-O-S as the cathode and active carbon as the anode had a high specific energy of 35 Wh/kg at a specific power of 903.2 W/kg, and possessed excellent long-term electrochemical cycling stability (95.2% capacitance retention after 10,000 cycles). These results indicate that our coralline composites provide a promising and feasible method for the development of supercapacitors.