Manganese oxides in-situ grown on carbon sphere and derived different crystal structures as high-performance pseudocapacitor electrode material

Abstract

The demand for energy storage equipment in the information age era is becoming increasingly scarce, but manganese-based metal oxides with large potential windows and multivalent states were developed and used as high-performance electrode materials for energy storage. MnO2 array grow on the carbon sphere as the precursor and then obtain multi-types and hierarchical of manganese metal oxides through gradient carbonization. The surface crystal phase changes with temperature, and the electrochemical performance shows obvious imparity. In addition, the carbon spheres gradually disappear with increasing temperature forming a hollow shell structure, which is conducive to sufficient contact between electrolyte and electrode material. It found that the annealing temperature can change the surface oxide morphology of MnO2/C, and it can know that the temperature promotes the conversion of MnO2 to Mn2O3 and Mn3O4. Based on the oxides of different crystal phases, the electrochemical properties are more distinctive due to their different structures. The rod-like nanoarray Mn2O3/C composites derived from annealing the precursors at 600 °C show high specific capacity and rate performance under a very large potential window of 0~1.2 V (show a remarkable specific capacitance of 277.0 F·g−1 at a current density of 1.0 A·g−1). Considering practical application, the as-assembles Mn2O3/C//Na2SO4//Mn2O3/C symmetrical supercapacitors device exhibits a maximum energy density of 80.35 Wh·kg−1 at a power density of 500 W·kg−1, which can be applied promising storage materials for information age.