Hierarchical copper cobalt sulfide nanobelt arrays for high performance asymmetric supercapacitors

Abstract

Hierarchical copper cobalt sulfide nanobelt array structures with well-defined morphology control are first reported as high energy density electrode materials for asymmetric supercapacitors using a simple two-step solvothermal method. Through appropriate control of the reaction time and sulfide ion concentration during the sulfidation reactions, saturated sulfidation was achieved while ensuring the morphology, structural integrity, and stability of the precursor. Subsequently, the unique morphological structure of the CuCo₂S₄ nanobelt arrays resulted in high availability and excellent conductivity of the electrochemically active sites. The CuCo₂S₄ electrode achieved a high specific capacity reaching 1014 C g⁻¹ at 1 A g⁻¹, and 1.95 C cm⁻² at 1 mA cm⁻² as well as excellent cycling stability of 93.82% after 5000 cycles at 20 mA cm⁻², superior to previous values for ternary transition metal sulfides. In addition, a stable output voltage with a 1.6 V aqueous asymmetric device was assembled using prepared mesoporous nitrogen-doped double-layer hollow carbon microspheres as the negative electrode and CuCo₂S₄ as the positive electrode. The assembled device exhibited a high energy density of 40.2 W h kg⁻¹ at a power density of 799.1 W kg⁻¹ with a high capacity retention (90.89% after 5000 cycles at 20 mA cm⁻²). More importantly, two devices in series could light up three red LEDs for more than 20 min and rotate a small motor for 15 s. Thus, the results of this study provide a strategy for the design and manufacture of other ternary metal sulfides for high-performance energy storage devices.