Bi-MOF Modulating MnO Deposition Enables Ultra-Stable Cathode-Free Aqueous Zinc-Ion Batteries.

The Mn-based materials are considered as the most promising cathodes for zinc-ion batteries (ZIBs) due to their inherent advantages of safety, sustainability and high energy density, however suffer from poor cyclability caused by gradual Mn dissolution and irreversible structural transformation. The mainstream solution is pre-adding Mn into the electrolyte, nevertheless faces the challenge of irreversible Mn consumption results from the MnO electrodeposition reaction (Mn  → MnO ). This work proposes a "MOFs as the electrodeposition surface" strategy, rather than blocking it. The bismuth (III) pyridine-3,5-dicarboxylate (Bi-PYDC) is selected as the typical electrodeposition surface to regulate the deposition reaction from Mn to MnO . Because of the unique less hydrophilic and manganophilic nature of Bi-PYDC for Mn , a moderate MnO deposition rate is achieved, preventing the electrolyte from rapidly exhausting Mn . Simultaneously, the intrinsic stability of deposited R-MnO is enhanced by the slowly released Bi from Bi-PYDC reservoir. Furthermore, Bi-PYDC shows the ability to accommodate H insertion/extraction. Benefiting from these merits, the cathode-free ZIB using Bi-PYDC as the electrodeposition surface for MnO shows an outstanding cycle lifespan of more than 10 000 cycles at 1 mA cm . This electrode design may stimulate a new pathway for developing cathode free long-life rechargeable ZIBs.