Hierarchical Fluorinated Polymer Separator Design Mitigating Bilateral Ionic Crosstalk in Aqueous Batteries

ABSTRACT Aqueous Zn//MnO ₂ batteries hold significant promise for safe and cost‐effective large‐scale energy storage, yet their practical deployment is hindered by rapid performance degradation. Here, we identify bilateral ionic crosstalk, a previously overlooked failure mechanism driven by active ion, as a root cause of electrode degradation. We demonstrate that excess Zn ²⁺ migrating from the anode induces irreversible phase transitions at the MnO ₂ cathode, forming electrochemically inert Zn _x (MnO ₂ ) _y phase (ZMO sclerosis). Concurrently, dissolved Mn ²⁺ from the cathode exacerbates corrosion and dendrite growth on the Zn anode. To mitigate this crosstalk, we design a hierarchical fluorinated polymer separator (HFPS). Such HFPS enables selective cation coordination and guides ion transport, achieving simultaneous regulation of Zn ²⁺ and Mn ²⁺ fluxes. This targeted regulation effectively mitigates ionic crosstalk and stabilizes both electrodes. Batteries employing the HFPS exhibit exceptional cycling stability, retaining 97% capacity after 1,000 cycles at 0.5 A g ⁻¹ with stable operation exceeding 500 h. This performance represents a 54% lifespan enhancement over state‐of‐the‐art aqueous counterparts. Our work provides a fundamental mechanistic understanding of active‐ion‐induced failure and establishes ion flux regulation as a universal design strategy for durable aqueous zinc‐ion batteries.