An Asymmetrical Supercapacitor Based on CNTs/SnO_2 and CNTs/MnO_2 Nanocomposites Working at 1.7 V in Aqueous Electrolyte

摘要

An asymmetrical supercapacitor was fabricated with a CNTs/SnO_2 negative electrode and a CNTs/MnO_2 positive electrode. It was tested in charge and discharge to 1.7 V in aqueous electrolyte without showing noticeable current resulting from water decomposition. Physicochemical properties of the CNTs/SnO_2 and CNTs/MnO_2 nanocomposites were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectrometry (EIS). At a current density of 0.25A g~(-1), the energy density of the hybrid supercapacitor was found to be 20.3 Whkg~(-1) which is comparable to that obtained from electric double layer supercapacitors using organic electrolytes (17~18Wh kg~(-1))~(1,2). The asymmetrical supercapacitor also shows exceptional stability over 1000 cycles with the capacity loss being less than 8%.