STRUCTURAL AND ELECTROCHEMICAL PROPERTIES OF LAYERED MANGANESE DIOXIDES IN RELATION TO THEIR SYNTHESIS - CLASSICAL AND SOL-GEL ROUTES

Specific structural, physical and electrochemical features of layered manganese dioxides either containing or not containing sodium, are exa mined and discussed in relation to their synthesis route: classical (p recipitation reactions) and sol-gel. Classical-route compounds give ri se to poor electrochemical behaviour, whereas sol-gel-route compounds are among the most promising rechargeable manganese dioxides for lithi um batteries. These results are related to the type of symmetry, which results from stacking of the layers, and to the nature of the host si te for the interlamellar cationic species. It is shown that the best c onditions for lithium electrochemical insertion correspond to the init ial existence of a hexagonal structure with trigonal prismatic sites.