Ion-Anchored Strategy for MnO/Mn Chemistry without "Dead Mn" and Corrosion.

The utilization of MnO/Mn chemistry in near-neutral pH acetate aqueous electrolytes provides an opportunity to achieve a higher energy density (theoretical capacity 616 mA h/g, discharge platform >1.5 V). However, this Zn-MnO aqueous battery suffers from inevitable "dead Mn" and proton corrosion. In this study, we discover that the diffusion of the cathode reaction intermediate Mn is intrinsic for the generation of "dead Mn", and the accumulation of "dead Mn" increases the H which shuttles to the anode, inducing serious corrosion. A pH-neutral hydrogel ion-anchored strategy is proposed here not only to restrict the diffusion of Mn but also to suppress the proton transference. This hydrogel ion anchor is designed by deprotonating a series of monomers undergoing in situ free radical polymerization at the cathode interface. The anionic monomer with a moderate binding energy to manganese ions is screened to anchor Mn, which enhances the reversibility of the MnO/Mn reaction. Simultaneously, a substantial amount of anionic groups and hydrophilic functional groups in the hydrogel effectively constrains the proton shuttle to corrode the anode. Consequently, the Zn/MnO battery achieves exceptional cyclic stability of the MnO/Mn reaction, sustaining 8500 cycles even at a relatively low current density and discharge current density of 1 mA/cm. Our findings highlight the importance of anchoring Mn at the cathode interface and offer valuable insights for advancing practical applications of MnO/Mn reactions.