MOF-derived carbon-coated NiS/NiS2 yolk-shell spheres as a satisfactory positive electrode material for hybrid supercapacitors

Abstract

Optimizing the performance of electrode materials to improve the energy density of supercapacitors is the focus of current research. Construction and design with complex yolk-shell structure, as a supercapacitor electrode material, are of great significance and challenging. Herein, a self-sacrificing template strategy was used to construct uniform carbon-modified NiS/NiS₂ yolk-shell spheres using a Ni-based metal–organic framework (Ni-soc-MOF) as the precursors. Especially, the carbon shells produced by the pyrolysis of the organic ligand can improve mechanical stability and electron conductivity. Therefore, the as-obtained NiS/NiS₂@C nanocomposites display a high specific capacity (1082 C g⁻¹at 1 A g⁻¹) and outstanding cycling stability (85% capacity retention after 5000 cycles). In addition, a hybrid supercapacitor device based on the yolk-shell NiS/NiS₂@C nanocomposite and porous carbon can deliver a high energy density of 56.2 Wh kg⁻¹ at 800 W kg⁻¹, while exhibiting an excellent capacity retention of 86% after 10,000 charge/discharge cycles, demonstrating the promising potential of yolk-shell NiS/NiS₂@C nanocomposites via Ni-soc-MOF-derived route in practical application.