Carbon/λ-MnO2 composites for supercapacitor electrodes

In the present work a composite of carbon with λ-MnO2 have been synthesized by a simple two-step route. In the first step, to obtain LiMn2O4/carbon material, mesoporous activated carbon was impregnated with the solution of precursor metal salts and heated subsequently. As-prepared materials were acid treated which resulted in the formation of λ-MnO2/carbon. Physical properties, structure and specific surface area of electrode materials were studied by TEM, X-ray diffraction and nitrogen sorption measurements. Voltammetry cycling, galvanostatic charge/discharge and impedance spectroscopy measurements performed in two- and three-electrode cells have been applied in order to measure electrochemical parameters. TEM images confirmed well dispersed λ-MnO2 particles on the surface of carbon material. The carbon in the composite plays an important role as the surface area enhancing component and a support of pseudocapacitive material. Furthermore, the through-connected porosity serves as a continuous pathway for electrolyte transport. A synergetic effect of the porous carbon framework and of the redox properties of the λ-MnO2 is at the origin of improvement of specific capacitance values which has been observed for composites after delithiation.

Comparison of capacitance characteristics for initial carbon and synthesised composites for CB in 1 mol L−1 Na2SO4 solution.Figure optionsDownload as PowerPoint slide