Achieving Highly Reversible Mn2+/MnO2 Conversion Reaction in Electrolytic Zn‐MnO2 Batteries via Electrochemical‐Chemical Process Regulation

Despite the widespread interest in electrolytic Zn‐MnO2 batteries with excellent output voltage and high theoretical capacity, the spontaneous disproportionation reaction of free Mn3+ along with the disorderly deposited inactive MnO2 results in the low Mn2+/MnO2 conversion reversibility, which seriously affects their cycling stability. Here, we propose a novel aqueous SiO2 colloidal electrolyte with FeSO4 mediator (denoted as SF electrolyte) based on a bidirectional electrochemical‐chemical model to achieve dual regulation of the MnO2 deposition/dissolution process. During the charging process, the SiO2 colloidal particles located at the carbon felt interface and the electrolyte bulk phase simultaneously provide sufficient disproportionation sites for the diffused Mn3+ to guide the orderly rapid deposition of MnO2. Meanwhile, the introduction of Fe2+ mediators during the discharge process can sufficiently react with MnO2 on the SiO2 particles in the electrolyte, thereby further enabling the efficient conversion of Mn2+/MnO2. Consequently, electrolytic Zn‐MnO2 battery with SF electrolyte can stably run for 550 cycles at 10 mA h cm‐2 and achieve superior reversibility at a high area capacity of 20 mA h cm‐2. This work demonstrates the feasibility of colloidal electrolytes in modulating electrochemical‐chemical processes to stabilize electrolytic Zn‐MnO2 batteries.