Seed-Assisted Reversible Dissolution/Deposition of MnO₂ for Long-Cyclic and Green Aqueous Zinc-Ion Batteries

Manganese oxide (MnO₂) based aqueous zinc-ion batteries (AZIBs) are considered to be a promising battery for grid-scale energy storage. However, they usually suffer from the great challenge of capacity attenuation due to Mn dissolution and irreversible structural transformation. Herein, full use of the shortcomings is made to design high-performance cathode-free AZIBs. Manganese-based Prussian blue analog (Mn-PBA) is selected as a seed layer to provide a stable MnO₂ electrodeposition surface. Thanks to the large specific surface area and manganophilic nature of Mn-PBA, the deposition/dissolution kinetics between Mn²⁺ and MnO₂ are significantly enhanced. Systematic studies revealed the mechanism of MnO₂ deposition-dissolution related to the reversible transformation of manganese oxide hydroxide and zinc hydroxide sulfate hydrate. Based on this, the developed cathode-free AZIBs exhibit outstanding rate performance (with a specific capacity of 273.7 mAh g^-1 at 1 A g^-1) and extraordinary cycle stability (maintaining a specific capacity of 52.3 mAh g^-1 after 50 000 cycles at 20 A g^-1). Furthermore, the AZIBs with non-toxic, biocompatible materials can be directly discarded after use, without causing pollution to the environment, which is expected to help achieve the sustainable development goals.