Surface design and engineering of ZnMn2O4/RGO composites for highly stable supercapacitor devices

The manipulation of phase and morphology of metal oxides by controlled engineering is considered to be a significant approach for enhancing electrochemical characteristics. The development of composite materials that are both highly efficient and cost-effective is crucial in the context of supercapacitors. A hydrothermal route is opted to fabricate ZnMn2O4/RGO microsphere electrodes. The control of process parameters during the synthesis and subsequent annealing allows for the development of microspheres exhibiting unique topographies of the surface. The incorporation of RGO into the composites has the potential to enhance conductivity, hence improving the overall utilization of the material. The ZnMn2O4/RGO composites exhibited the specific capacitances of 628, 545, 488, 446, 380 and 364 F g−1 at current densities of 1, 2,3,5,10 and 20 A g−1, respectively. Furthermore, the results demonstrated exceptional rate capability as the material retained 58 % of its initial capacitance even under a high current density. In addition, it retained a capacitance of 95.2 % even after 10,000 cycles at 1 A g−1. Furthermore, ZnMn2O4/RGO@ASC device displayed a reasonable specific capacitance of 128.7 F g−1 at 1.5 A g−1 and retained a capacitance of 83.9 % for 5000 cycles at 5 A g−1. The ZnMn2O4/RGO@ASC device had the energy density of 40.2 W h kg−1 at a power density of 1125 W/ kg. As a result, developed supercapacitor devices are preferred for use in portable electronics and industrial applications.