A Polyzwitterionic “Ion‐Sponge” Interphase via In Situ Self‐Polymerization for Ultradurable Zinc Batteries

ABSTRACT Aqueous zinc batteries hold great potential for grid storage applications; however, their practical deployment is severely limited by parasitic side reactions and uncontrollable dendrite formation. Herein, we design a polyzwitterionic “ion‑sponge” interphase via an in‑situ self‑polymerization strategy. Specifically, under electric‑field induction, zwitterion monomers polymerize into an ultrathin polyzwitterion layer that electrostatically enriches anions (OTf − , SO 4 2 − ) and excludes water at the interface. This unique microenvironment enables the in‑situ reductive conversion of anions into ZnF 2 and ZnS. The resulting polyzwitterion–ZnF 2 /ZnS hybrid SEI enhances both the uniformity of Zn 2 + deposition and the Zn 2 + migration rate. The interfacial Zn 2 + diffusion coefficient reaches 1.9 × 10 − 4 cm 2 s − 1 (100 times higher than the bulk). Consequently, Zn||Zn symmetric cells stably cycle for over 1000 h at 5 mA cm − 2 and 5 mAh cm − 2 , and also for over 5500 h at −20 °C. Full cells with V 2 O 5 cathode achieve a high average capacity of 339 mAh g − 1 and 99.9% Coulombic efficiency over 1900 cycles, along with stable low‑temperature operation. This polyzwitterionic “ion‑sponge” interphase concept provides in‑depth insights into interfacial ion transport regulation for high‑performance aqueous zinc batteries.