One-step electrochemical synthesis of alpha-MnO2 and alpha center dot gamma-MnO2 compounds for lithium batteries

Manganese dioxides of the alpha- structure type or interconnected alpha- an d gamma -phases (noted as alpha . gamma) have been prepared from acidic MnS O4 solutions. using the electrochemical method. The structure of the materi al obtained, gamma -MnO2. alpha -MnO2, or alpha . gamma -MnO2, can be contr olled by adjusting the temperature, the acidity of the solution. or the app lied current. This is the first report of the electrochemical synthesis of alpha -MnO2 without "stabilizing" cations such as K+. The Li insertion beha vior of the alpha -MnO2 and alpha . gamma -MnO2 synthesized here is promisi ng, showing a reversible capacity in the range of previously reported alpha -MnO2 and very good cyclability. (C) 2001 The Electrochemical Society.