Inherently porous Co3O4@NiO core–shell hierarchical material for excellent electrochemical performance of supercapacitors

Supercapacitors have become a highly appealing candidate for next-generation energy storage system due to their high power density and long operation life. However, insufficient active materials utilization leads to a relatively low specific capacitance, which poses a significant challenge to their practical applications. In our work, hierarchical nanostructure with intrinsic porous NiO nanosheets uniformly dispersion on Co3O4 backbone is prepared through a facile and environmentally friendly method (denoted as Co3O4@NiO-X). The resulting well-defined porous core–shell material (Co3O4@NiO-1) displays a three-dimensional architecture, convenient ion transport channel and more exposed surface area, which demonstrates a significantly enhanced pseudocapacitance performance, with a high specific capacitance (692.8 F/g at a current density of 1 A/g) and excellent cycling performance (90.88% of initial value is retained after 2500 cycles). Furthermore, an asymmetric supercapacitor (ACS) is fabricated by employing Co3O4@NiO-1 core–shell material as positive electrode, activated carbon (AC) as negative electrode and 6 M KOH as electrolyte, which represents an excellent specific capacitance of 68.1 F/g (at 1 A/g) and provides high energy density of 35 Wh/kg at the power density of 540 W kg−1, 23.4 Wh/kg at higher power density of 2722.1 W/kg, together with exceptional cyclic stability of 90.83% after 3000 cycles. The excellent electrochemical performance of Co3O4@NiO-1 materials demonstrates that rational design of porous core–shell structure can be a general strategy for multi-component materials to realize electrochemical energy storage devices with excellent performance.