Unraveling the Pseudocapacitive Charge Storage Mechanism of NiCo2O4 Nanoflakes for Advanced Quasi Solid-State Hybrid Supercapacitor

Abstract

Design and development of battery-type electrode materials with high capacitance, wide potential window, and desirable cycle stability are essential to enhance the performance of hybrid supercapacitors (HSC). In this study, a simple sol-gel synthesis strategy has been adopted to fabricate spinel NiCo2O4 nanoflakes. The morphological and structural analysis shows that the NiCo2O4 is formed with nanoflakes morphology having high phase purity and good stoichiometry. The electrochemical study of the NiCo2O4 electrode in 1 M Na2SO4 aqueous electrolyte reveals that the electrode has a maximum specific capacitance of 488 F g−1 at 2 A g−1. Detailed electrochemical examinations of cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS) profiles reveal the pseudocapacitive charge storage kinetics of NiCo2O4 electrode. Furthermore, a hybrid supercapacitor device is constructed by employing molybdenum-disulfide (MoS2) & reduced graphene oxide (rGO) nanocomposite and NiCo2O4 as the negative and positive electrodes, respectively. PVA-Na2SO4 is utilized as the polymer gel electrolyte. The HSC device delivered the highest specific capacitance of 106 F g−1 at a current density of 0.8 A g−1 with superior cyclic stability. Thus, exploring strategies for superior performance through material modification and selection of suitable electrolyte has been useful and makes this study significant among the reported related works.