Core–shell structured Co₃O₄@NiCo₂O₄ electrodes grown on Ni foam for high-performance supercapacitors

Recently, supercapacitors (SCs) have emerged as one of the most promising energy storage devices, which can be attributed to their exceptional power density, rapid charge–discharge rate, and superior cycling stability. Despite the progress made in the signal metal oxide of SCs, several challenges still need to be addressed, including the poor electrical conductivity, unsatisfactory cyclic stability, and low energy density. It is crucial to develop innovative composite materials with synergistic effects to address these issues. In this study, the cobalt oxide and Co₃O₄@NiCo₂O₄ composite were successfully synthesized on Ni foams by a hydrothermal method. Composite electrodes featured by the hierarchical core–shell structures were identified as an effective approach for improving the electrochemical performance of SCs. Noteworthily, the as-fabricated core–shell structures demonstrated excellent specific capacitance of 1514 F g⁻¹ at a current density of 1 A g⁻¹, a stable operating voltage of 0–0.5 V and outstanding cycling stability (with almost no attenuation after 2000 cycles at a charge–discharge current density of 10 A g⁻¹). The enhanced electrochemical behavior can be attributed to the synergistic effect between two electrode active materials and the presence of more electron and ion transport pathways. The as-prepared composite electrodes can be considered as the potential electrode materials for energy storage applications.