Multifunctional Interfacial Engineering Enables Stable MnO₂ Cathodes for Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc-manganese dioxide (Zn-MnO₂) batteries are one of the most promising candidates for large-scale energy storage due to their advantages of high safety, a high operating potential, and low cost. However, the unstable interface reactions and low electrical conductivity of the MnO₂ cathode hold significant obstacles for the electrochemical performance of Zn-MnO₂ batteries. Herein, we report a unique interfacial engineering approach to cooperatively tackle with Mn²⁺/MnO₂ chemistry and build a conductive network at the electrode-electrolyte interface for the MnO₂ cathode through dual-layer coating of ZIF-8/polypyrrole on MnO₂ (ZPM). The outer ZIF-8 coating layer helps maintain a dynamically stable dissolution/deposition of Mn²⁺, whereas the electronic conductive polypyrrole inner layer establishes a robust conductive network. As a result, the ZPM cathode demonstrates an exceptional rate performance and a prolonged lifespan of 5000 cycles with a low attenuation of 0.00925% per cycle at 10C. The ampere-hour pouch cell of the ZPM cathode achieves a total capacity of 1068.4 mAh under a high areal capacity of 2.5 mAh cm^-2, validating its practical viability. This dual-layer interfacial engineering strategy integrating Mn²⁺ dissolution/deposition regulation and electronic conductivity optimization provides an insightful pathway for addressing the complex issues of aqueous Zn-MnO₂ batteries.