Facile design and synthesis of a nickel disulfide/zeolitic imidazolate framework-67 composite material with a robust cladding structure for high-efficiency supercapacitors.

In this paper, a core-shell structure nickel disulfide and ZIF-67 composite electrode material (NiS/ZIF-67) was synthesized by a two-step method. Firstly, spherical NiS was synthesized by a hydrothermal method, dispersed in methanol, then reacted and coated by adding cobalt ions and 2-methylimidazole to obtain the NiS/ZIF-67 core-shell composite. The NiS/ZIF-67 composite shows a high specific capacitance (1297.9 F g at 1 A g) and excellent cycling durability (retaining 110.0% after 4000 cycles at 5 A g). Furthermore, the corresponding hybrid supercapacitor (NiS/ZIF-67//AC HSC) has an energy density of 9.5 W h kg at 411.1 W kg (6 M KOH) and remarkable cycling stability (maintaining 133.3% after 5000 cycles). Its excellent electrochemical performance may be due to the core-shell structure and the synergistic effect between the transition metal sulfide and metal-organic framework. These results indicate that the NiS/ZIF-67 composite as an electrode material with a core-shell structure has potential application in high-efficiency supercapacitors.