Synthesis of CuS and CuS/C-150 for application in battery type electrode and analysis via electrochemical impedance spectroscopy

In this work, a simple and efficient hydrothermal synthesis route for CuS and CuS/C-150 is presented, overcoming the limitations of traditional methods by using a single-step synthesis that allows more efficient and scalable process. This method also provides a more detailed study of the mechanisms between the material/electrolyte interface through electrochemical impedance spectroscopy. Scanning electron microscopy analyses revealed the morphological formation of microspheres and microsheets under the synthesis conditions. The method and synthesis conditions led to the formation of CuS in the covellite form (JCPDS nº 06–0646), which was confirmed via X-ray diffraction. A decrease in the intensity of the peaks in the CuS/C-150 diffractogram was observed, characteristic of amorphous material. Cyclic voltammetry revealed redox peaks characteristic of CuS and CuS/C-150 materials, and the specific capacity values of CuS and CuS/C-150 were measured by galvanostatic charge–discharge, yielding 168.8 and 121.9 C.g⁻¹, respectively. These values indicate that these materials are good charge storage. For cyclic stability (5 mA.cm⁻²), CuS/C-150 retained 74.1% after 200 cycles. Electrochemical impedance spectroscopy analysis indicated that the resistances were negligible for both solution and charge transfer. Through complex calculations via impedance spectroscopy, the materials obtained relaxation time constants (τ₀) of approximately 2.30 s, and at the intercept of the |Q/S| =|P/S|, 70% curves were obtained. Therefore, the electrochemical results were satisfactory and confirmed that the materials are promising battery-type electrodes and that the hydrothermal route is viable and effective for obtaining the studied materials.