Cobalt-Doped MnO2 Hierarchical Yolk-Shell Spheres with Improved Supercapacitive Performance

摘要

Cobalt-doped MnO2 with a hierarchical yolk-shell spherical structure has been prepared by a light-assisted method. The hierarchical spheres obtained are characterized by X-ray diffraction, nitrogen adsorption-desorption, and electron microscopy analyses. The supercapacitive performance of the material is evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements. A specific capacitance of 350 F g(-1) is achieved at a current density of 0.1 A g(-1) for the spheres with a Co/Mn ratio of 0.5%, much higher than that of the undoped MnO2 with a similar hierarchical spherical structure, which is approximately 168 F g(-1). A specific capacitance of 196 F g(-1) is still retained after being charged/discharged at a current density of 2.0 A g(-1) for 1000 cycles, demonstrating good cycling stability. Over 90% of the initial specific capacitance was retained, exhibiting excellent capacitance retention ability.