Coordination Bridges in Confined‐Water Domains Enable Partially Desolvated Zn 2 + Transport in Aqueous Zinc‐Ion Batteries

ABSTRACT Zinc‐ion batteries (ZIBs), owing to their intrinsic safety and cost competitiveness, are attracting significant interest as next‐generation energy storage system (ESS) technologies. However, their commercialization is severely hindered by poor cycle stability, primarily originating from dendritic Zn growth and parasitic hydrogen evolution. To address these challenges simultaneously, we design and integrate a multifunctional polymeric protective layer incorporating amide and imidazolium functional groups. The zincophilic amide groups facilitate ion transport by providing stable Zn 2+ binding sites, whereas the hygroscopic imidazolium groups establish a confined‐water domain that regulates local solvation dynamics. Within this domain, water molecules transiently stabilize Zn 2+ and act as a coordination bridge during ion migration, yet their mobility toward the electrode surface is restricted. This dual functionality increases the Zn 2+ single‐ion conductivity 6.55‐fold and reduces the hydrogen evolution rate by 79.1%. Consequently, Zn//Zn symmetric cells exhibit markedly extended cycling lifetimes of up to 2200 h at 1 mA cm −2 and 1 mAh cm −2 . When applied to Zn–I 2 full cells, the protective layer enables stable operation over 4000 cycles with >85% capacity retention, even under a practical areal capacity of 3.6 mAh cm −2 . These findings highlight a robust interfacial strategy to realize long‐duration, high‐capacity aqueous ZIBs for grid‐scale energy storage.