Synthesis of MnO2 nanostructures with MnS-deposits for high performance supercapacitor electrodes

Abstract

We report the synthesis of MnO₂ nanostructures with MnS deposits via a facile one-step hydrothermal process for high-performance supercapacitor applications. In comparison to pure MnO₂ nanoflowers, MnS deposition substantially alters the morphology of the MnO₂ nanoflowers with respect to the addition of the sulfur source. The crystalline nature and changes in morphology of the synthesized composite materials were confirmed by powder XRD and FESEM analysis. The electrochemical behaviors were examined by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy techniques in 1 M Na₂SO₄ aqueous electrolytes. The 3MnS/MnO₂ nanocomposite exhibits a relatively high specific capacitance of 384.25 F g⁻¹ at a current density of 1 A g⁻¹, which is nearly two-fold higher than that of pure MnO₂ nanoflowers (204.25 F g⁻¹). A symmetric capacitor was fabricated using the 3MnS/MnO₂ nanocomposite and activated carbon as positive and negative electrodes, respectively. The resulting asymmetric device exhibits a specific capacitance of 84.56 F g⁻¹ at a current density of 0.5 A g⁻¹ and a cycle stability of ∼87% after 1000 charge–discharge cycles.