CuCo2S4–MoS2 nanocomposite: a novel electrode for high-performance supercapacitors

Abstract

Ternary transition metal sulfides have emerged as promising electrode materials for next-generation supercapacitors because of their potential ability to simultaneously ensure high conductivity and stability during electrochemical reactions. In the present investigation, MoS₂ incorporated CuCo₂S₄ nanocomposites have been successfully synthesized using a hydrothermal technique. The structural, morphological, elemental and chemical properties of the prepared CuCo₂S₄–MoS₂ nanocomposite were investigated extensively. High resolution transmission electron microscopy imaging demonstrated the successful synthesis of CuCo₂S₄–MoS₂ nanocomposites. The electrochemical capacitor performance of the nanocomposite has been evaluated both in three-electrode and symmetric two-electrode systems. In the three-electrode cell, a specific capacitance of 820 F g⁻¹ was achieved for the CuCo₂S₄–MoS₂ electrode at a current density of 0.5 A g⁻¹ which is considerably higher than that of the CuCo₂S₄ electrode (249 F g⁻¹). We observed that the charge storage capacity, conductivity and stability of CuCo₂S₄ improved significantly due to the incorporation of MoS₂. Finally, an asymmetric supercapacitor was fabricated by assembling the CuCo₂S₄–MoS₂ electrode with an activated carbon electrode which demonstrated a large stable working potential window of 1.6 V. Excellent long-term cyclic stability of 89% retention after 1000 galvanostatic charge-discharge cycles was evident. As a solid state device, it delivered a high energy density of 38.22 W h kg⁻¹ at a power density of 400 W kg⁻¹ and lit up one red LED for 170 s, indicating its superiority over the conventional Cu-Co based supercapacitors.