Facile synthesis of nanorod-assembled multi-shelled Co₃O₄hollow microspheres for high-performance supercapacitors

In this work, we report a novel strategy for the controlled synthesis of nanorod assembled multi-shelled cobalt oxide (Co₃O₄) hollow microspheres (HSs). The Co₂CO₃(OH)₂NRs are first vertically grown on the carbon microspheres (CS) to form the core-shelled composites by a low-temperature solution route. The multi-shelled hollow interiors within the Co₃O₄microspheres are unconventionally obtained by annealing the as-prepared core-shell structured CS@Co₂CO₃(OH)₂composite in air. When evaluated for supercapacitive performance, the multi-shelled Co₃O₄hollow microspheres exhibit high capacitance of 394.4 and 360 F g^-1at the current densities of 2 A g^-1and 10 A g^-1, respectively. The superior electrochemical performance can be attributed to the multi-shelled hollow structures, which facilitate the electrolyte penetration and provide more active sites for the electrochemical reactions.