Synergistic Effect of CoNiS@FeOOH Hybrid Nanostructured Sheets for Enhanced Battery-Type High Energy Density Performance

In this study, the synthesis of highly redox-active CoNiS@FeOOH hybrid nanostructures (HNSs) containing ultrathin nanosheet-oriented hybrid flower-like structures aimed for enhanced energy storage performance in supercapacitors (SCs). The unique hierarchical Co-Ni-S-based nanostructures facilitate abundant active sites, a rich redox nature, and excellent electrical conductivity, resulting in a battery-type behavior and enabling easy charge transfer and good electrochemical stability. The battery-type behavior of the highly redox-active CoNiS@FeOOH HNS electrode achieved a high specific capacity of 1873 C/g (3122 F/g) with a rate capability of 75.7%, revealing excellent energy storage performance. Furthermore, the CoNiS@FeOOH//AC solid-state supercapacitor device exhibited a high energy density of 132 Wh/kg and a high-power density of 3800 W/kg with 98% capacitance retention and 99% Coulombic efficiency over 10,000 GCD cycles. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of multiple oxidation states, which allow redox reactions and enhance charge storage. Comprehensive electrochemical examinations reveal outstanding capacitive behavior, low resistance, and high-rate capability. These findings position CoNiS@FeOOH as a promising candidate for the development of high-performance energy storage devices.