Hierarchical Mn(2)O(3) Microspheres In-Situ Coated with Carbon for Supercapacitors with Highly Enhanced Performances

Porous Mn(2)O(3) microspheres have been synthesized and in-situ coated with amorphous carbon to form hierarchical C@Mn(2)O(3) microspheres by first producing MnCO(3) microspheres in solvothermal reactions, and then annealing at 500 °C. The self-assembly growth of MnCO(3) microspheres can generate hollow structures inside each of the particles, which can act as micro-reservoirs to store biomass-glycerol for generating amorphous carbon onto the surfaces of Mn(2)O(3) nanorods consisting of microspheres. The C@Mn(2)O(3) microspheres, prepared at 500 °C, exhibit highly enhanced pseudocapacitive performances when compared to the particles after annealed at 400 °C and 600 °C. Specifically, the C@Mn(2)O(3) microspheres prepared at 500 °C show high specific capacitances of 383.87 F g(−1) at current density of 0.5 A g(−1), and excellent cycling stability of 90.47% of its initial value after cycling for 5000 times. The asymmetric supercapacitors assembled with C@Mn(2)O(3) microspheres after annealed at 500 °C and activated carbon (AC) show an energy density of up to 77.8 Wh kg(−1) at power density of 500.00 W kg(−1), and a maximum power density of 20.14 kW kg(−1) at energy density of 46.8 Wh kg(−1). We can attribute the enhanced electrochemical performances of the materials to their three-dimensional (3D) hierarchical structure in-situ coated with carbon.