An investigation on layered birnessite type manganese oxides for battery applications

Layered birnessite-type manganese oxide was prepared by a simple redox sol-gel reaction involving hydroxylamine and permanganate in alkaline medium. IR, XRD, Auger electron spectroscopy, EPR, TGA and cyclic voltammetric characteristics of the birnessites are presented. The birnessite was examined for its cathode performance in zinc-, magnesium- and lithium-based cells. Bismuth and lead exchanged birnessite show superior battery performance when compared with sodium and potassium precursors. The magnetoresistance pattern of the discharged birnessite (in Mg/Mg(ClO4)(2)) indicates a colossal magnetoresistance, This observation provides a scope for further studies of examining the applicability of magnetoresistance measurement in assessing the charge/discharge status of manganese oxides. Heat treatment of birnessite brings about distinct changes in the EPR and IR pattern. A correlation between the spectral features and electrochemical activity can be understood. (C) 2000 Elsevier Science S.A. All rights reserved.