Crystallinity‐Induced Ion Rectification in Polymer/Zn Interphases for Stable Aqueous Zinc Batteries

The energy density and cycle life of aqueous zinc metal batteries are hindered by inherent chemical and mechanical instabilities at the Zn/electrolyte interface, causing uncontrolled dendrite formation and side reactions. Here, an anisotropic crystalline polymer interphase by leveraging the hierarchical structure to stabilize the interface is designed. The stabilization effect strongly depends on the crystallinity of polymer chains, where the one with optimal ion transfer possesses a preferred orientation of nanocrystals parallel to the Zn anode. This topological structure creates fast tunnel for ion transport that significantly enhances the kinetics and reversibility of electrochemical transformations. The ordered crystalline phase and disordered amorphous phase respectively blocks H₂O penetration and provides Zn²⁺ transport channels, reaching an optimum between electrode protection and ion transfer. Symmetric cells with the crystallinity-tuned interface demonstrate an exceptionally long lifespan exceeding 3000 h at elevated current density and capacity of 5 mA cm^-2 and 5 mAh cm^-2, with a cumulative plated capacity of 7500 mAh cm^-2. The Zn/AC hybrid ion supercapacitor exhibits outstanding stability, enduring over 10 000 cycles at 5 A g^-1. The work unveils new ordering-dependent ion transport in solid-state polymer interphase/electrolyte and provides a feasible approach for advancing grid-scale aqueous batteries.