Mn_3-x Fe_x O₄ Hollow Nanostructures for High-Performance Asymmetric Supercapacitor Applications

Design of hollow nanostructure and controllable phase of mixed metal oxides for improving performance in supercapacitor applications is highly desirable. Here we demonstrate the rational design and synthesis of Mn_3-x Fe_x O₄ hollow nanostructures for supercapacitor applications. Owing to high porosity and the specific surface area that provides more active sites for electrochemical reactions, the electrochemical performance of Mn_3-x Fe_x O₄ hollow nanostructure substantially enhanced comparing with pristine Mn₃ O₄ . Particularly, in 1.0 M KOH electrolyte, Mn_0.16 Fe_2.84 O₄ with a typical diameter of 20 nm exhibits excellent specific capacitance of 2675, 2320, 1662, 987 F g^-1 at current densities of 1, 2, 5, 10 A g^-1 , respectively, which is significantly superior to those of other transition metal oxides. Besides, an asymmetric supercapacitor is assembled by using Mn_0.16 Fe_2.84 O₄ and activated carbon as a positive and a negative electrode, respectively. Electrochemical results indicate a high energy density of 42 Wh kg^-1 at a power density of 0.75 kW kg^-1 , which makes this hollow nanostructure a highly promising electrode for achieving high-performance next-generation supercapacitors.