The back-deposition of dissolved Mn 2+ to MnO 2 cathodes for stable cycling in aqueous zinc batteries.

The Mn 2+ dissolution of MnO 2 cathode materials causes rapid capacity decay in aqueous zinc batteries. We herein show that the dissolved Mn 2+ 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 MnO 2 /Mn 2+ redox process also provides capacity. In the Mn 2+ free ZnSO 4 electrolyte, MnO 2 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 MnO 2 cathodes in aqueous zinc batteries without Mn 2+ additives.