Ion‐Sieving Effect Enabled by Sulfonation of Cellulose Separator Realizing Dendrite‐Free Zn Deposition

Abstract Aqueous zinc‐ion batteries (AZIBs) hold great potential for grid‐scale energy storage systems, owing to their intrinsic safety and low cost. Nevertheless, their industrialization faces challenges of severe Zn dendrites and parasitic reactions. In this study, sulfonated cellulose separator (denoted as CF‐SO3) with low thickness, exceptional mechanical strength, and large ionic conductivity is developed. Benefiting from the electrostatic repulsion between ─SO3− functional groups and SO42− anions and the strongly interaction between ─SO3− and Zn2+ cations, the migration of SO42− anions can be restricted, the 2D diffusion of Zn2+ ions at the surface of Zn electrode can be suppressed, and the desolvation of hydrated Zn2+ ions can be promoted. Concurrently, the homogeneous nanochannels within CF‐SO3 separator can ensure uniform electric field and Zn2+ ion flux. With these benefits, the CF‐SO3 separator enables Zn//Zn cells to run stably for 1200 h at 4 mAh cm−2 by facilitating oriented and dendrite‐free Zn deposition. Under a large depth of discharge of 68.3%, a life span of 400 h can still be achieved. Additionally, the reliability of CF‐SO3 separator is confirmed in Zn//MnO2 and Zn//H11Al2V6O23.2 full batteries with high mass loading conditions. This work provides valuable guidance for the advancement of high‐performance separators of AZIBs.