CHEMICALLY ACTIVATED MANGANESE-DIOXIDE FOR DRY BATTERIES

The present investigation has enabled us to convert inactive beta-mang anese dioxide to high electrochemically active types by chemical proce sses. Natural and chemically prepared beta-manganese dioxides were roa sted at 1050-degrees-C to form Mn3O4. This compound was subjected to a ctivation treatment using hydrochloric and sulfuric acid under various reaction conditions. The manganese dioxide so obtained was examined b y X-ray diffraction, thermogravimetric, differential thermal and chemi cal analyses. The structure of the dioxide obtained was found to be gr eatly dependent on the origin of MnO2 and type of acid used. Treatment with hydrochloric acid yield the so-called gamma-variety while sulfur ic acid tended to produce gamma- or alpha-MnO2. In addition, waste man ganese sulfate obtained as by-product from sulfuric acid digestion tre atment was recycled and electrolytically oxidized to gamma-MnO2. The d ischarge performance of the above-mentioned MnO2 samples as battery ca thodic active material was evaluated and compared with the ordinary ba ttery grade.