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

Abstract

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.