Regulation Effects of Co2+ in Constructing of Cu-Ni(OH)2@CoO Nanoflower Clusters Heterojunction: A Critical Factor of Obtaining High-Performance Battery-type Hybrid Supercapacitor
The electrode material with hierarchical nanostructure derived from transition metal-based compound is an important branch of energy storage materials and has attracted widespread attention in recent years. Herein, the Cu-Ni(OH)2@CoO nanoflower clusters (Cu-Ni(OH)2@CoO NFCs) heterojunction is successfully constructed by a simple two-step hydrothermal method in the presence of Co2+. The optimized Cu-Ni(OH)2@CoO NFCs presents a high capacitive performance and outstanding cycle stability when used as a battery-typed supercapacitive electrode material. Specifically, an ultra-high areal specific capacitance of 5.8 F cm-2 (354.8 mAh g-1) at 1 mA cm-2 was obtained in the 3 M KOH electrolyte. Even after 10,000 cycles, the capacitance still remains 98.4% of its initial value. All experimental characterization results indicate that the excellent performance of Cu-Ni(OH)2@CoO NFCs self-supporting electrode is attributed to the regulatory effect of Co2+ on morphology and electronic structure, which is induced by the second hydrothermal process. More specifically, the transformations in morphology and electronic structure will expose more active sites and accelerate charge transferring during the electrochemical reaction. Besides, the rapid oxidation reactions of multivalent transition metal ions and enhanced hydrophilicity promotes the electrochemical reaction kinetics processes on the Cu-Ni(OH)2@CoO NFCs electrode. This work provides a promising strategy for exploring low-cost and efficient electrode materials based on transition metal compounds in electrochemical energy storage.