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

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.