An investigation of the electrochemical characteristics of NiO-Co₃O₄/graphite/PVDF composites for the development of a supercapacitor with ultrahigh stability

Abstract Supercapacitors are a groundbreaking electrical energy storage technology that falls between batteries and dielectric capacitors which has undergone significant progress in recent years. Among the several elements influencing a supercapacitor’s capacitance, the choice of electrode materials plays a crucial role. Nanomaterials formed from transition metal oxides (TMOs) with incorporated 3D graphite are said to possess high capacitance, conductivity, increased active site area, distinct redox properties and several valence shells, making them an appropriate material for electrode synthesis. Therefore, in this study, three composites of NiO and Co 3 O 4 are prepared in the ratio of 2:8, 3:7 and 4:6 using facile sol–gel method. To the prepared composites, graphite and PVDF are added in equal quantities. The resultant samples are characterized using XRD, SEM, FTIR and UV–vis spectroscopy. The samples are further integrated on an FTO electrode and subjected to CV, GCD and EIS for electrochemical study. The highest specific capacitance is obtained for NiO and Co 3 O 4 composite in the ratio 3:7 and is equal to 156.66 F g −1 at a sweep rate of 10 mV s −1 . This material is further subjected to a two-electrode study to check its feasibility to develop a symmetric solid-state device. It demonstrated a specific capacitance of 36 F g −1 with 100% capacitive retention.