Rattle-type NiCo₂O₄-carbon composite microspheres as electrode materials for high-performance supercapacitors

In this work, NiCo₂O₄-carbon composite microspheres with rattle-type structure were successfully prepared by a template-engaged hydrothermal and subsequent calcination treatment. These rattle-type microspheres are composed of a solid carbon core and a porous shell with nanorods as building blocks. The calcination temperature of the NiCo₂O₄-carbon precursor has an obvious effect on the morphology as well as the resultant capacitive performances. Because of their unique structure and high specific surface area, these rattle-type NiCo₂O₄-carbon composite microspheres exhibited excellent electrochemical performances with high specific capacitance (790 F g^-1 at 1 A g^-1), and it even reached as high as 609 F g^-1 at 10 A g^-1. Additionally, excellent cycling stability with 99.4% specific capacitance retention after continuous 2000 cycles at a current density of 2 A g^-1 was observed, suggesting their promising application in supercapacitors. The synergistic effect of different components and the rattle-type structure may contribute to the outstanding performance of the composite electrode.