Reducing Manganese Dissolution in Electrolytic Manganese Dioxide Electrodes in NaOH Electrolyte

Abstract

Previous attempts to enhance the stability and performance of MnO2-based cathodes for use in aqueous alkaline electrolytes, primarily KOH-based, have relied on a range of additives. This work demonstrates that the fast capacity decay of the MnO2-based cathode materials in alkaline electrolytes is mainly due to spontaneous manganese dissolution when cycling through the second-electron reaction voltage range. Reducing relative electrolyte content and using carbon materials that have a high specific surface area suppresses manganese dissolution and thus extends the cycle life of the electrode material while reducing overall battery costs. Moreover, reducing the size of the MnO2 particles and decreasing the cycling rate are found to increase manganese dissolution and negatively impact the performance of the electrode material, indicating a sensitivity to material surface area. Lastly, Fe-MnO2-based low-cost battery chemistry was also demonstrated based on the second electron reaction of the MnO2 in an electrolyte lean environment, which could be promising for grid-level energy storage.