Co-doped nickel sulfide (NiS2) derived from bimetallic MOF for high-performance asymmetric supercapacitors

The optimization of the material structure and the adjustment of the components are effective ways to improve the energy storage performance of the electrochemical capacitors. In this study, the core-shell cobalt-doped nickel sulfide microspheres with a reasonable structure were designed and constructed, and the morphological changes of the material were investigated by adjusting the Co/Ni ratio. The core-shell bimetallic sulfide microspheres were prepared by a two-step method without templates. In the first step, the core-shell Ni-Co MOF was obtained by a hydrothermal method. In the second step, Co-doped NiS2 was obtained by using sulfur powder as sulfur source and heating at high-temperature under the protection of nitrogen. The special structure of the bimetallic sulfide showed excellent electrochemical properties with the specific capacitance of 332.8 mA h g−1 at 1 A·g−1. The cycle stability was maintained at 84.9% after 5000 cycles. The two-electrode system condition test showed that the energy density of ASD reached 65.6 Wh kg−1 when the power density was 0.85 kW kg−1, indicating that the material is a promising material for energy storage devices.