Pseudocapacitive behaviors of nanostructured manganese dioxide/carbon nanotubes composite electrodes in mild aqueous electrolytes: effects of electrolytes and current collectors

Abstract

Nanostructured MnO2/carbon nanotubes composite electrode material was prepared using the liquid-phase deposition reaction starting with potassium permanganate (KMnO4) and manganese acetate (Mn(Ac)2·4H2O) as the reactants and carbon nanotubes (CNTs) as the substrates. The structure and morphology of the material was characterized by X-ray diffraction, infrared spectroscopy, and transmission electron microscope techniques. The electrochemical properties of the nano-MnO2/CNTs composite electrode in 1 M LiAc and 1 M MgSO4 solutions and in 1 M RAc (R = Li, Na, and K)–1 M MgSO4 mixed solutions, respectively, were studied. Experimental results demonstrated that the specific capacitance and rate discharge ability of the nano-MnO2/CNTs composite electrode in 1 M LiAc–1 M MgSO4 mixed solution is superior to that in 1 M LiAc or 1 M MgSO4 solution. For the 1 M RAc (R = Li, Na, and K)–1 M MgSO4 mixed electrolytes, the specific capacitance of the composite electrode was found to be in the following order: LiAc > NaAc > KAc.