PREPARATION AND ELECTROCHEMICAL-BEHAVIOR OF DOPED MANGANESE-DIOXIDE

Doped manganese dioxides were prepared by homogeneous hydrolysis and oxidation of manganese(III)-compounds. Three sets of conditions were employed: (a) oxidation and hydrolysis in acid medium, (b) oxidation and hydrolysis in basic medium, (c) oxidation in acid and hydrolysis in basic medium. Doping elements were Mg, Ca, Sr, Ba, Al, Fe, Ni, Zn. All precipitates were essentially amorphous. The discharge capacity of products from (a) varied between 44 and 48 mAh/g except for the Al-doped product, which, as the number of cycles increases, displays a continuous improvement of capacity up to 65 mAh/g, producing a hard discharge curve. Products from (C) are remarkable with respect to both discharge capacity and cycle stability; the product doped with Ba had 91 mAh/g discharge capacity and this value remained constant for 320 cycles.