Self-assembled Zn-Co MOF nanospheres/rGO as cathode material for an asymmetric supercapacitor with high energy density

The bimetal-constructed metal-organic frameworks (MOFs) were developed to enhance the structural stability and synergistic effects of individual metals used in energy storage and conversion. However, the choice of metal species is critical and strict. Inspired by the MOF synthesis, Zinc and Cobalt are assembled as nodes combined with the ligands in the MOF configuration to form the Zn-Co nanosphere structures, which are then connected with rGO sheets. As a result, the faradaic process of cobalt and high property of zinc enable Zn-Co nanosphere/rGO (Zn-Co NS/rGO) to exhibit significant supercapacitor electrode performance, with 2925 F g−1 at 0.5 A g−1, and a considerable rate capability of 45.4% capacitance at a high current density of 50 A g−1. Subsequently, the Zn-Co NS/rGO is utilized to fabricate an asymmetric supercapacitor that matches up with a 3D rGO aerogel anode. The fabricated device shows outstanding properties, including an enlarged operating potential window of 1.5 V, an energy density of 43.04 W h kg−1 at a power density of 900 W kg−1, and 14.166 W h kg−1 at 75,000 W kg−1, plus a capacitance retention of 96% after 10,000 charge-discharge cycles test at 10 A g−1.