Loosening Zinc Ions from Separator Boosts Stable Zn Plating/Striping Behavior for Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries are attracting broad interest in stationary energy storage where low cost, robust security, and satisfactory capacity matter most. However, metal zinc anodes suffer from destructive dendrite issues during repeated charging/discharging process, decreasing the cycle life of batteries. Herein, smoother zinc plating/striping behaviors are achieved by group modification in the structural unit of the polymer separator. Experimental results and theoretical simulations reveal that the polymer skeleton can release zinc ion more easily when modified with carbonylation side groups and contribute to much faster zinc ion transfer capability. Typically, symmetric Zn cells with a thin thickness separator of 21 µm exhibit ultralong cycle life over 2800 h at 1 mA cm⁻² within 1 mAh cm⁻² and 300 h under a high current density of 5 mA cm⁻² within high areal capacity of 3 mAh cm⁻². Full cells using a sodium vanadium oxide cathode also show stable reversible charging/discharging performance after 2000 cycles at 3 A g⁻¹. This work is expected to inspire promising strategies in molecular design in polymeric separator toward stabilizing metal anodes beyond this anode itself.