Safe, economical and fast-charging secondary batteries using single-walled carbon nanotubes

Abstract

We developed a new concept aqueous electrolyte secondary battery by combining redox reactions of iodide ions in single-walled carbon nanotubes (SWCNTs) and alkali metal ions with quinone molecules. The new concept battery consisting only of abundant elements utilizes the fast ion movements of both the cation and anion in a safe aqueous electrolyte medium. As active quinone molecules, anthraquinone (AQ) and 9,10-phenanthrene quinone (PhQ) were used. AQ and PhQ molecules were inserted in SWCNTs because the electric conductivities of AQ and PhQ molecules are insufficient as battery electrode materials. Both redox reactions of the cation and anion of an alkali metal halide aqueous electrolyte were investigated by electrochemical measurements such as cyclic voltammetry and chronopotentiometry. The redox reaction of iodide ion was observed by chronopotentiometry as a very flat charge/discharge potential plateau at about 0.45 V vs. Ag/AgCl. On the other hand, PhQ redox reactions showed gradient potential plateau. It was also found that the discharge plateau potential of PhQ electrode measured with NaI aqueous electrolyte is about 0.1 V lower than that with LiI.