Surface analysis on discharged MnO2 cathode using XPS and SIMS techniques

Manganese dioxide (MnO₂) appears to be an effective cathode material for a battery system. No studies on lithium insertion in aqueous media are known to the best of our knowledge. However, in one of our previous papers we reported that lithium could be intercalated into a MnO₂ host compound using an aqueous LiOH electrolyte; however simple chemistry suggests that it should not. It is found that a battery with LiOH electrolyte functions quite differently from the cell that uses Li₂SO₄. This paper describes the surface modifications that accompany the electrochemical behavior of MnO₂ during redox (discharge) processes in the lithium hydroxide and sulfate media. XPS and SIMS techniques were used to study the resultant surface of the MnO₂ cathode and the spectra reveal that the formation of an insoluble layer of Li₂CO₃ precedes the process of reduction. SEM was used to study the microstructure of the MnO₂ cathode. Copyright © 2008 John Wiley & Sons, Ltd.