Molecular Engineering of Conjugated Polymer Cathodes via One-Pot Preparation for High-Rate and Ultra-Stable Aqueous/Seawater Zn-Ion Batteries under Harsh Conditions

Abstract

Organic materials are promising candidates for high-performance aqueous Zn-ion batteries (AZIBs) cathodes owing to their high capacity, structural adjustability, and sustainability. However, their practical application is hindered by limited redox activity and low electronic conductivity under harsh operating conditions. Here, we report an organic polymer cathode using a simple one-pot preparation, poly (Mellitic Trianhydride-Phenazine) (PMPZ), featuring a fully conjugated structure and abundant active functional groups. The incorporation of heterocyclic conjugated unit into the conjugated structure enhances electron affinity and π-electron delocalization of polymer, resulting in high redox activity and significantly elevated conductivity. Meanwhile, multiple C=O and C=N redox-active centers act cooperatively to enable multielectron redox process through this delocalization pathway, improving the charge storage and reaction kinetics. Through combined theoretical and operando synchrotron experimental studies, we further elucidate that this fully conjugated structure facilitates reversible Zn2+/H+ co-storage with multiple electron transfer. Consequently, the PMPZ cathode demonstrates exceptional electrochemical performance with remarkable rate capability and outstanding cycling stability across a wide temperature range from −50 to 50 °C, even at seawater-based electrolytes. This work provides a novel design strategy for developing high-performance AZIB cathodes capable of operating under extreme conditions.