Realizing Lean‐Electrolyte Zinc‐Ion Batteries via An Ultrathin and Cost‐Effective Separator

Ultrathin separators accompanied with lean electrolyte conditions are highly desirable for developing high‐energy‐density aqueous Zn‐ion batteries (AZIBs). Herein, a 10 µm separator (PGZ) is designed via a facile and cost‐effective strategy. Experiments and theoretical simulations demonstrated that high polar β ‐PVDF in PGZ separator permits rapid Zn 2+ transfer while blocking OTf – , I 3 – , I 5 – , and H 2 O, effectively homogenizing the Zn 2+ flux, preventing polyiodide shuttle, and suppressing parasitic reactions. Moreover, the ultrathin separator enables a reduced electrolyte usage to 2 µL mg −1 , significantly increasing the energy density. Consequently, Zn/Zn symmetric cells with the PGZ separator stably cycle for 3500 h at 0.5 mA cm −2 @0.5 mAh cm −2 . The Zn/I 2 full cells exhibit ultralong cyclic stability over 23 000 cycles at 5C (≈240 days). Even at harsh conditions of high I 2 loading (10.4 mg cm −2 ), low E/A ratio (2 µL mg −1 , electrolyte volume per active material), and low N/P ratio (3.9), superior cycling performance (2750 cycles with 93.1% capacity retention) and high gravimetric energy density (129.7 Wh kg −1 ) are obtained. This work presents a simple and cost‐effective strategy for designing ultrathin separators for achieving stable lean‐electrolyte and high‐energy‐density AZIBs.