Three-Dimensional Crosslinked Nanosheet/Nanoparticle Composite CuS Electrode for Supercapacitors

As excellent energy storage devices, supercapacitors (SCs) have received widespread attention. Designing a reasonable SC device structure and exploring better active electrode materials are important ways to improve the electrochemical performance of supercapacitors. CuS electrodes were prepared in situ on a brass substrate by using an in situ chemical reaction method. The impact of the temperature and duration of concentrated hydrochloric acid treatment on the electrode materials was examined. Morphological and compositional analyses of the CuS electrode materials were conducted using SEM, EDS, XRD, Raman spectroscopy, and XPS. The electrochemical properties were assessed through CV, GCD, and EIS. By utilizing a 70 min treatment with concentrated HCl at 78 °C, CuS materials exhibiting nanosheet/nanoparticle composite morphologies were synthesized. The nanoparticles were approximately 10 nm in diameter, while the nanosheets, which were interconnected to form honeycomb structures, were 300 nm in diameter and 10 nm in thickness. When the current density was set at 5 mA cm–2, the area-specific capacitance of the CuS electrode reached 1814 mF cm–2. An asymmetric supercapacitor, CuS∥rGO, was fabricated by using the aforementioned conditions for the anode and rGO for the cathode. This configuration achieved a surface capacitance of 256 mF cm–2 at a current density of 2 mA cm–2. The maximum energy density attained was 0.05 mWh cm–2, with a peak power density of 12.15 mW cm–2. After 10,000 constant current charge–discharge cycles, the capacity retention rate reached 74%, while the Coulombic efficiency remained above 96%.