Electrolytic manganese dioxides for battery applications: studies using electron paramagnetic resonance

Electron paramagnetic resonance (EPR) date are presented for four different samples of electrolytic manganese dioxide (EMD) that are intended for use in battery applications. The effects of graphite addition and discharge of active material are examined. Amongst the samples, wide differences in both the intercrystalline parameters and the number of available electrons in the conduction band are observed. The g factor is found to exhibit sensitive variations from sample to sample. In some samples, several types of manganese electrons can be detected. The extent of the γ phase — an essential aspect for aqueous electrochemical activity — can be assessed in samples. MnO₂-graphite agglomerates and reduction products of MnO₂ are identified. The magnetism of active materials is explained from analysis of the EPR spectra.