Needle-like nanostructured Mn3O4@MnO2/C composites with boosted electrochemical performance as high-performance supercapacitor electrodes

Abstract

In recent years, manganese oxide/carbon composites with excellent electrochemical properties have attracted widespread interest as a result of synergistic effect. In this work, a kind of needle-like Mn₃O₄@MnO₂/C composite electrode is successfully developed. First, the MnO₂/C composites are prepared by using the preferred polyimide/20 %KMnO₄ composites as precursors, followed by carbonization at 800 °C. Then, the needle-like Mn₃O₄@MnO₂/C composites are obtained after hydrothermal reaction of the ground MnO₂/C particles and KMnO₄. The influence of weight ratio of KMnO₄ to MnO₂/C on the microstructures and electrochemical properties of the final composites is investigated. The three-electrode test results reveal that the Mn₃O₄@MnO₂/C-(3:1) shows a capacitance value of 717.9 F g⁻¹ (199.4 mAh g⁻¹), superior to the specific capacitance of MnO₂/C about 460.9 F g⁻¹ (128.0 mAh g⁻¹) at 0.5 A g⁻¹. After the Mn₃O₄@MnO₂/C-(3:1) is assembled into symmetric supercapacitors (SC), the SC exhibits an energy density of about 21.0 Wh kg⁻¹, higher than the MnO₂/C with 11.4 Wh kg⁻¹ at 250 W kg⁻¹. Over 10,000 charging-discharging cycles, the final specific capacitance can maintain 94 % of the original capacitance, suggesting excellent long-term cycling stability. Thus, the present study reports a feasible method to prepare Mn₃O₄@MnO₂/C composites with superior electrochemical performance as SC electrodes.