An extra-long-life supercapacitor based on Co3O4/NiCo2O4/NiO/C&S composite by decomposition of Co/Ni-based coordination complex

Highlights: • A tightly packed Co₃O₄/C&S nanocomposite is fabricated by a coordination precursor. • The composite shows extra-long cycling stability (>20,000 cycles). • This improvement in the cycle life is attributed to its highly stable structure. • The continuous C and S play a key role in forming of the tightly packed structure. Single-material electrodes do not satisfy the demands of high-performance supercapacitors. To exploit the advantages of both oxides and carbon-based materials, a tightly packed Co₃O₄/NiCo₂O₄/NiO/C&S nanocomposite is fabricated by sintering a Co/Ni-based coordination complex precursor at 400 °C. The composites and basic components are characterized using various techniques, namely, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area analysis, and elemental analysis. The electrochemical performance is analyzed by cyclic voltammetry, galvanostatic charge/discharge cycling, and electrochemical impedance spectrometry. A uniform nanocomposite was found to be formed of NiCo₂O₄, NiO, and Co₃O₄ nanoparticles, incompletely carbonized C, and incompletely vulcanized S. When used as supercapacitor electrodes, the synthesized composites show extra-long cycling stability (>20,000 cycles) during the charge/discharge process. This improvement in the cycle life of the composites is attributed to its highly stable structure. The roles of C and S in forming a stable structure are investigated. The results show that a supercapacitor with electrodes made from the as-prepared Co₃O₄/NiCo₂O₄/NiO/C&S composite will be promising for commercial applications.