Aqueous zinc/manganese batteries have drawn wide attention due to their low cost, high capacity, and are environmentally benign. A newly developed battery based on redox conversion between Mn²⁺ and MnO₂ has been reported. Since the two-electron redox reaction is involved in this type of battery, it provides a high theoretical capacity of 616 mAh g⁻¹ for MnO₂, which is twice as conventional insertion/extraction zinc ion batteries. However, Mn²⁺/MnO₂ dissolution-deposition type batteries are limited by the low coulombic efficiency at high areal capacity applications. The increasing loading mass and thickness of MnO₂ on the conductive substrate lead to exfoliation and incomplete dissolution. Both problems cause capacity loss and become more severe at a high charge/discharge rate, hindering these batteries from practical use.

To alleviate the problems mentioned above, the distribution of deposited MnO₂ should be more even to avoid large deposition thickness in part. This study introduced nucleation sites onto carbon fibers to improve deposited MnO₂ uniformity. The morphology of MnO₂ is controlled in granular shape by adding a proper amount of a specific cation into an aqueous electrolyte. This improvement makes MnO₂ exfoliation less and lets dissolution be more complete. As a result, the coulombic efficiency can be enhanced significantly. The distribution and morphology of deposited MnO₂ were investigated with a scanning electron microscope. Galvanostatic charge/ discharge cycle measurements characterized the electrochemical properties. These results provide great insight into the detailed reaction mechanism of dissolution-deposition battery reaction mechanisms and the strategies to improve both Coulombic efficiency and cycling stability.