Nano copper cobaltite/manganese sulfide, (1−x)CuCo₂O₄/xMnS (x = 0.0, 0.25, 0.5, 1) samples were synthesized applying thermolysis and hydrothermal process. Phase identification using x-ray diffraction and Rietveld analysis disclosed single-phase CuCo₂O₄ (CCO) for intermediate samples (x = 0.25, 0.5) implying that MnS phase is not formed. X-ray photoelectron spectroscopy (XPS) analysis proved incorporation of Mn and S into the CCO lattice forming a solid solution. The transmission electron microscope revealed homogenous nanoparticle morphology with a small range size distribution. XPS measurements unveiled the cation oxidation states of the constituent elements Co²⁺/Co³⁺, Cu²⁺/Cu⁺ and Mn²⁺/Mn³⁺ providing abundant redox electron pairs. The specific capacitance (C_s) obtained from cyclic voltammetry (CV) and galvanostatic charge/discharge (GSCD) curves is noticeably increased after the addition of MnS. The best electrochemical performance was obtained by the solid solution 0.75CuCo₂O₄/0.25MnS with a specific capacitance of 674 Fg⁻¹ and high cycling stability. The electrochemical impedance spectroscopy (EIS), the Nyquist curves and the equivalent circuit for the 0.75CuCo₂O₄/0.25MnS solid solution electrode were discussed.

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