Achieving Highly Reversible Mn/MnO Conversion Reaction in Electrolytic Zn-MnO Batteries via Electrochemical-Chemical Process Regulation.

Despite the widespread interest in electrolytic Zn-MnO batteries with excellent output voltage and high theoretical capacity, the spontaneous disproportionation reaction of free Mn along with the disorderly deposited inactive MnO results in the low Mn/MnO conversion reversibility, which seriously affects their cycling stability. Here, we propose a novel aqueous SiO colloidal electrolyte with FeSO mediator (denoted as SF electrolyte) based on a bidirectional electrochemical-chemical model to achieve dual regulation of the MnO deposition/dissolution process. During the charging process, the SiO colloidal particles located at the carbon felt interface and the electrolyte bulk phase simultaneously provide sufficient disproportionation sites for the diffused Mn to guide the orderly rapid deposition of MnO. Meanwhile, the introduction of Fe mediators during the discharge process can sufficiently react with MnO on the SiO particles in the electrolyte, thereby further enabling the efficient conversion of Mn/MnO. Consequently, electrolytic Zn-MnO battery with SF electrolyte can stably run for 550 cycles at 10 mAh cm and achieve superior reversibility at a high area capacity of 20 mAh cm. This work demonstrates the feasibility of colloidal electrolytes in modulating electrochemical-chemical processes to stabilize electrolytic Zn-MnO batteries.