The back-deposition of dissolved Mn2+ to MnO2 cathodes for stable cycling in aqueous zinc batteries

The Mn2+ dissolution of MnO2 cathode materials causes rapid capacity decay in aqueous zinc batteries. We herein show that the dissolved Mn2+ can be deposited back to the cathode with the aid of a suitable conductive agent. The active material is thus retained for energy storage, and this MnO2/Mn2+ redox process also provides capacity. In the Mn2+ free ZnSO4 electrolyte, MnO2 delivers 325 mA h g-1 capacity at 0.1 A g-1, and 90.4% capacity retention is achieved after 3000 cycles at 5 A g-1. Our work demonstrates an effective strategy to realize stable cycling of MnO2 cathodes in aqueous zinc batteries without Mn2+ additives.