Microwave assisted reflux synthesis of NiCo2O4/NiO composite: Fabrication of high performance asymmetric supercapacitor with Fe2O3

NiCo2O4/NiO nanocomposite is successfully synthesized by rapid microwave assisted reflux method at various reaction times. XRD analysis is performed to reveal the crystalline nature and the compound formation. Further, the chemical environment of the surface composition of NiCo2O4/NiO is identified by X-ray Photoelectron spectroscopy. The morphological analysis (FESEM and TEM) of the composite showed that the formation of bundle like irregular large aggregates, which consists of nearly spherical particles. The maximum specific capacitance of 1924 F g−1 at 1 mV s−1 in 1 M KOH electrolyte with an excellent energy density of 75 Wh Kg−1 at a power density of 103 W kg−1 is revealed for the NiCo2O4/NiO electrode. An asymmetric supercapacitor (ASC) is constructed using optimized NiCo2O4/NiO as positive and synthesized Fe2O3 as negative electrodes. This novel NiCo2O4/NiOǁFe2O3 architecture provides superior capacitive performance with a specific capacitance of 417 F g−1 at 1 mV s−1. Subsequently the charge-discharge analysis exhibits the specific capacitance of 79 F g−1 at 1 mA cm−2. The fabricated asymmetric supercapacitor (ASC) delivers an energy density of 19 Wh kg−1 at 157 W kg−1. Moreover, it provides an excellent cycle stability of about 97% capacitance retention over 5000 cycles.