Carbon nanocoils decorated with a porous NiCo2O4 nanosheet array as a highly efficient electrode for supercapacitors

Abstract

Well-organized substrate materials are of considerable significance in the development of energy-efficient pseudocapacitor electrodes. Herein, functionalized three-dimensional (3D) carbon nanocoils on nickel foam (CNCs/NF) have been used as the substrate to grow faradaic nickel cobaltite (NiCo₂O₄) via a solvothermal method. The arrays of NiCo₂O₄ were assembled by interconnected ultrathin nanosheets with random inter-particle pores. The number of electroactive sites increased specifically because of the porous feature of NiCo₂O₄ nanosheets and the 3D structure of CNCs/NF. Moreover, the CNCs/NF network aided the electrolyte ions in diffusing deeply within the architecture. The NiCo₂O₄/CNCs/NF composite exhibited an outstanding specific capacitance of 2821 F g⁻¹ at the current density of 1 A g⁻¹, a remarkable rate capability (82.4%) and long cyclic stability (91.7% after 3000 cycles). Such encouraging electrochemical performance was attributed mainly to the synergistic interactions of NiCo₂O₄ arrays and CNCs/NF substrate that helped achieve efficient redox reactions, enhanced ion diffusivity and excellent electron conductivity. In summary, this binder-free NiCo₂O₄/CNCs/NF composite electrode paves a way towards the synthesis of highly efficacious electrodes for supercapacitors.