Preparation of the Active Manganese(IV) Oxide for Dry Batteries by the Thermal Decomposition of Manganese(II) Sulfate

Abstract

The purpose of this study is to produce battery-grade active manganese(IV) oxide by thermal decomposition of manganese(II) sulfate. Anhydrous manganese(II) sulfate was first decomposed at 1000°C in air to form trimanganese tetraoxide and then heated again at 700-800°C in air to obtain manganese(III) oxide. The interfacial reaction was concluded to be the rate-determining step of the overall oxidation process. The remnant after extraction of the manganesea sulfate from the manganese=oxide with hot sulfuric acid was γ-type manganese(II) oxide. This oxide showed a high discharge activity equal to or superior to that for the electrolytic manganese(IV) oxide. The apparent specific volume was large than that for the electrolytic manganese(IV) oxide and was almost equal to that for the activated manganese(IV) oxide ore.