Hierarchical CoO@Ni(OH)₂ core–shell heterostructure arrays for advanced asymmetric supercapacitors

Constructing multicomponent electrode materials with a rational structure is an effective route to develop high-performance supercapacitors. We herein report a novel nickel-foam-supported hierarchical CoO@Ni(OH)₂ nanowire-nanosheet core–shell heterostructure array synthesized by a facile hydrothermal-electrodeposition strategy. The core CoO nanowire arrays with good electrical conductivity and shell Ni(OH)₂ nanosheets with thickness of ∼ 2 nm synergistically contributes to increased active sites, fast mass transfer, and improved structural stability. Consequently, the optimal CoO@Ni(OH)₂–400 s architecture delivers a high specific capacitance of 1418.2 F g⁻¹ at 1 A g⁻¹ and 93.7% retention after 5000 cycles. Furthermore, the CoO@Ni(OH)₂//activated carbon asymmetric supercapacitor could achieve an outstanding energy density of up to 92.47 W h kg⁻¹ at 800 W kg⁻¹. This simple but effective strategy provides insight into the development of core–shell hierarchical architectures for constructing high-performance supercapacitors. (paper)