Electrolyte-Induced Interfacial ZnMn₂O₄ Formation on MnO₂@MOF-5 Cathodes for Ultra-Stable Aqueous Zinc-Ion Batteries

In aqueous zinc-ion batteries (AZIBs), enhancing electrochemical stability through interfacial engineering has gained significant attention. This study introduces an interfacial phase reconstruction strategy by leveraging the confined induction capability of MOF-5. Mn^{2 +} ions preloaded in the electrolyte (2 M ZnSO₄ and 0.2 M MnSO₄) preferentially engage with Zn^{2 +} at the MOF-5 surface, forming a dynamic and reversible in situ ZnMn₂O₄ interphase that enhances the performance and stability of AZIBs. ZnMn₂O₄ functions as a self-expanding, reversible interfacial host that is vital for managing energy storage and ensuring structural stability. The presence of MOF-5 provides confined nucleation sites that enable the selective deposition of ZnMn₂O₄, thereby protecting the underlying MnO₂ from collapse and dissolution. With this dynamic interfacial engineering, the CC/MO@MOF-5 electrode demonstrates a reversible capacity of 173.7 mAh g^{- 1} at 0.1 A g^{- 1} and gradually activates to 79 mAh g^{- 1} after 5000 cycles at 1 A g^{- 1}. The electrochemical reversibility of ZnMn₂O₄ and its voltage-dependent phase evolution are systematically investigated. This work redefines ZnMn₂O₄ as a tunable and electrochemically active main storage phase and establishes an electrolyte-interphase co-design strategy for aqueous multivalent ion batteries under extreme conditions.