Construction of flower-like ZnCo₂S₄/ZnCo₂O₄ arrays on Ni foam for high-performance asymmetric supercapacitors

The high-energy density of supercapacitors is urgently needed. In this work, we develop a high energy density hierarchical ZnCo₂S₄/ZnCo₂O₄ electrode material with flower-like structure directly anchored on nickel foam by hydrothermal and ion exchange method. The as-prepared hierarchical arrays take advantage of ZnCo₂S₄ with high electroactive surface area, flower-like morphology with rapid channels for ion diffusion and electron transport. ZnCo₂O₄ possesses good stability and cooperativity with ZnCo₂S₄. Remarkably, the ZnCo₂S₄/ZnCo₂O₄ delivers a specific capacitance of 1057.78 F g⁻¹ at the current density of 1 A g⁻¹ in a three-electrode system. An asymmetric supercapacitor (ASC) was assembled with ZnCo₂S₄/ZnCo₂O₄ as positive electrode and carbon nanotubes (CNTs) as negative electrode, delivers a high energy density of 127.4 W h kg⁻¹ at a power density of 2520 W kg⁻¹ and a long cycle life (89% of capacity retention after 5000 cycles). The assembled ASC can work as a power source, which can drive the fan after being charged.