A Polyzwitterionic "Ion-Sponge" Interphase via In Situ Self-Polymerization for Ultradurable Zinc Batteries

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^-, SO₄ ^{2 -}) and excludes water at the interface. This unique microenvironment enables the in‑situ reductive conversion of anions into ZnF₂ and ZnS. The resulting polyzwitterion-ZnF₂/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} cm² 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 V₂O₅ 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.