Effect of Manganese Valence on Specific Capacitance in Supercapacitors of Manganese Oxide Microspheres

Manganese oxides have attracted great interest in electrochemical energy storage due to high theoretical specific capacitance and abundant valence states. The multiple valence states in the redox reactions are beneficial for enhancing the electrochemical properties. Herein, three manganese microspheres were prepared by a one-pot hydrothermal method and subsequent calcination at different temperatures using carbon spheres as templates. The trivalent manganese of Mn₂ O₃ exhibited multiple redox transitions of Mn³⁺ /Mn²⁺ and Mn⁴⁺ /Mn³⁺ during the intercalation/deintercalation of electrolyte ions. The possible redox reactions of Mn₂ O₃ were proposed based on the cyclic voltammetry and differential pulse voltammogram results. Mn₂ O₃ microsphere integrated the advantages of multiple redox couples and unique structure, demonstrating a high specific capacitance and long cycling stability. The symmetric Mn₂ O₃ //Mn₂ O₃ device yielded a maximum energy density of 29.3 Wh kg^-1 at 250 W kg^-1 .