Heat treated electrolytic manganese dioxide for Li/MnO2 batteries: effect of precursor properties

The present study demonstrates that the properties of heat-treated electrolytic manganese dioxide (EMD) materials can be linked to the key properties of the precursor EMD used. The investigation holds particular significance for the informed selection of precursor EMD materials that result in superior performing heat treated materials in Li/MnO₂ batteries. Kinetic analysis is used to determine the precise heating regime necessary to, theoretically, completely remove structural water from six different EMD samples. It was found that the oxidation of Mn(III) to Mn(IV) occurred to a greater extent for samples with initially high pyrolusite content and a low fraction of cation vacancies after heat treatment at low temperatures. This same Mn(III) to Mn(IV) conversion was also enhanced after high temperature treatment for those samples with a higher manganese content and low cation vacancy fraction. Additionally, at low heat treatment temperatures the parent γ-MnO₂ structure and cation vacancies were better retained in samples with low starting BET surface area. Finally, this work determined that samples with high BET surface area tend to lose proportionally less of this value as a consequence of heat treatment, compared to those with low initial values.