Comparison of pH 6 potentials, alkaline potentials and initial open circuit voltages of electrolytic MnO2

Abstract

The alkaline battery industry typically reports three electrolytic MnO2 (EMD) potentials: alkaline potentials, pH 6 potentials, and initial open circuit voltages (IOCV). These measurements differ with the electrolyte, the reference electrode, and the cathode composition. Despite such physical differences, theoretical relationships exist between the electrolytic potentials that are verifiable by experiment. The calculated difference (alkaline potential − pH 6 potential) is 0.785 V, which compares favourably with the experimental value of 0.795 ± 0.003 V. Another difference (alkaline potential − IOCV) depends on carbon-induced EMD reduction, which varies with EMD type and graphite:EMD ratio. After determining the carbon effect experimentally and graphically estimating [ZnO22−], (alkaline potential − IOCV) was calculated as −0.045 V. This is roughly 60 mV from the experimental value of +0.017 V. Our analysis shows that when the differences in electrolyte and cathode compositions, and reference electrodes, are accounted for, the three EMD potentials are equivalent.