Synthesis of Carbon-Based Spinel NiCo₂O₄ Nanocomposite and Its Application as an Electrochemical Capacitor

Abstract

In this study, a thermal method was used to synthesize spinel NiCo₂O₄ and carbon nanotubes (CNTs)@NiCo₂O₄ with an average size 50 nm and 20 nm, respectively. Addition of CNTs into NiCo₂O₄ noticeably increases the active surface area compared to pure spinel NiCo₂O₄. SEM analyses showed that the morphologies are spherical in both pure and composite samples. Uniform CNTs@NiCo₂O₄ nanoparticles exhibit high specific capacitance of 210 F g⁻¹ at 2 A g⁻¹ and a good retention capacity of 92.70% after 2500 cycles, which shows a considerable improvement compared to NiCo₂O₄. Additionally, an exceptional rate capability of about 73.2% was obtained at 50 A g⁻¹. Such remarkable electrochemical performance of the CNTs@NiCo₂O₄ can be attributed to high specific surface area and also uniform structure which increase the exposure of active sites available for reaction on the surface shortened transport pathways for both electrons and ion. Also, volume change during the charge-discharge process is mainly alleviated compared to pure spinel NiCo₂O₄. A carbonaceous material such as the CNT facilitates the charge transfer and improves the stability of frame against volume change.