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

Abstract Despite the widespread interest in electrolytic Zn‐MnO 2 batteries with excellent output voltage and high theoretical capacity, the spontaneous disproportionation reaction of free Mn 3+ along with the disorderly deposited inactive MnO 2 results in the low Mn 2+ /MnO 2 conversion reversibility, which seriously affects their cycling stability. Here, we propose a novel aqueous SiO 2 colloidal electrolyte with FeSO 4 mediator (denoted as SF electrolyte) based on a bidirectional electrochemical‐chemical model to achieve dual regulation of the MnO 2 deposition/dissolution process. During the charging process, the SiO 2 colloidal particles located at the carbon felt interface and the electrolyte bulk phase simultaneously provide sufficient disproportionation sites for the diffused Mn 3+ to guide the orderly rapid deposition of MnO 2 . Meanwhile, the introduction of Fe 2+ mediators during the discharge process can sufficiently react with MnO 2 on the SiO 2 particles in the electrolyte, thereby further enabling the efficient conversion of Mn 2+ /MnO 2 . Consequently, electrolytic Zn‐MnO 2 battery with SF electrolyte can stably run for 550 cycles at 10 mAh cm −2 and achieve superior reversibility at a high area capacity of 20 mAh cm −2 . This work demonstrates the feasibility of colloidal electrolytes in modulating electrochemical‐chemical processes to stabilize electrolytic Zn‐MnO 2 batteries.