THE EFFECT OF POTASSIUM ON THE PHYSICAL, CHEMICAL AND STRUCTURAL PROPERTIES OF ELECTROLYTIC MANGANESE DIOXIDE (EMD). V.Ichharam, A.W.Bryson, D.Levendis, F.Crundwell, Centre for Molecular Design, University of the Witwatersrand, Private bag 3, Wits, 2050, Gauteng, South Africa

EMD is used as a cathode material in batteries. X-ray powder diffraction was used to analyse the structure of K⁺ doped EMD. Results confirm that K⁺ induces cryptomelane formation. The current work shows that K⁺ induces the formation of two structural forms of cryptomelane. These structural forms are the monoclinic and tetragonal forms which have similar unit cell parameters. XRD analysis of solid EMD fragments showed that cryptomelane tends to form on a relatively pure [[gamma]]-MnO₂ substrate. Supporting data was obtained using Energy Dispersive X-ray Analysis (EDXA). XRD data along with data reported in the literature (Kao et al.) and data obtained from techniques such as BET surface area measurement and standard compositional analysis techniques permitted a structural model for K⁺ doped EMD to be proposed. In this model K⁺ ions are located primarily in tunnels of the cryptomelane structure which forms a part of the EMD matrix.

Kao, W.H. et al. (1987). J.Electrochem.Soc. 134(6). 1322-1325; (1992) J.Electrochem.Soc. 139(5). 1223-1226.