One-pot synthesis of copper oxide–cobalt oxide core–shell nanocactus-like heterostructures as binder-free electrode materials for high-rate hybrid supercapacitors

Hierarchical mesoporous nanocactus-like copper oxide–cobalt oxide (CuO–CoO) core–shell architectures are directly grown on nickel foam by a facile, scalable, and cost-effective one-pot hydrothermal technique followed by thermal annealing and directly served as efficient electrode materials for hybrid supercapacitors (HSCs). The CoO nanoneedles are uniformly decorated on the surface of CuO nanoflakes to generate core–shell-like heterostructures. The CuO nanoflakes offer the abundant electroactive sites and enables fast redox reactions, while the CoO nanoneedles facilitates electrolyte diffusion and charge transportation, resulting superior rate capability and cycling life. Accordingly, the hierarchical core–shell CuO–CoO electrode achieves a specific capacity of 173.9 mA h g⁻¹ at 1 A g⁻¹ and long-cycle life with 94% retention over 5000 cycles at 4 A g⁻¹. Moreover, the fabricated HSC exhibits a stable operating voltage window of 1.6 V, excellent energy density of 56.5 W h kg⁻¹, respectively. Also, the HSC delivers a superior cycling stability of 98.8% retention with coulombic efficiency of 98.7% over 4000 cycles, implying the great potential for practical applications.