Synthesis and electrochemical characterizations of amorphous manganese oxide and single walled carbon nanotube composites as supercapacitor electrode materials

Abstract

Long cycle performance at a high charge–discharge current of 2 A/g for the amorphous MnO 2 (a-MnO 2) and single walled carbon nanotubes (SWNTs) composites have been studied for the first time. The a-MnO 2 and SWNT composites have been successfully synthesized via a novel room temperature route starting with KMnO 4, ethanol and commercial SWNTs. Homogeneity of the synthesized composites was established by electron microscopic studies. Electrochemical properties of the synthesized composites were elucidated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. All the composites with different SWNT loads showed excellent cycling capability, even at the high current of 2 A/g, with the MnO 2:20 wt% SWNT composite showing the best combination of coloumbic efficiency of 75% and specific capacitance of 110 F/g after 750 cycles. However, the composite with 5 wt% SWNTs showed the highest specific capacitance during initial cycles.