Facile design and synthesis of a nickel disulfide/zeolitic imidazolate framework-67 composite material with a robust...

In this paper, a core-shell structure nickel disulfide and ZIF-67 composite electrode material (NiS₂/ZIF-67) was synthesized by a two-step method. Firstly, spherical NiS₂ was synthesized by a hydrothermal method, dispersed in methanol, then reacted and coated by adding cobalt ions and 2-methylimidazole to obtain the NiS₂/ZIF-67 core-shell composite. The NiS₂/ZIF-67 composite shows a high specific capacitance (1297.9 F g^-1 at 1 A g^-1) and excellent cycling durability (retaining 110.0% after 4000 cycles at 5 A g^-1). Furthermore, the corresponding hybrid supercapacitor (NiS₂/ZIF-67//AC HSC) has an energy density of 9.5 W h kg^-1 at 411.1 W kg^-1 (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 NiS₂/ZIF-67 composite as an electrode material with a core-shell structure has potential application in high-efficiency supercapacitors.