Strong polymer-cellulose interfacial engineering enables hydrogel-enhanced separators with multiscale networks for zinc-ion batteries.

Cellulose paper-based separators have attracted significant attention as promising materials for aqueous zinc ion batteries (ZIBs) owing to their excellent wettability, chemical stability, and environmental compatibility. However, water molecules penetrate into the amorphous regions of cellulose to induce plasticization, thus increasing the mobility of molecular chains and disrupting the intermolecular hydrogen bonding within cellulose. This degradation mechanism severely deteriorates battery cycling performance and capacity retention, thereby hindering the utility of cellulose paper-based separators in aqueous ZIBs. Herein, we propose an in situ photo-initiated radical polymerization strategy to integrate acrylamide-nanocellulose hydrogels onto cellulose separators, resulting in the construction of hydrogel-coated composite separators. In this design, the strong polymer-cellulose interfacial interactions restrict cellulose chain mobility, homogenize Zn ion flux, and significantly enhance wet-state mechanical robustness. Consequently, the composite separator ensures structural integrity during prolonged cycling. The assembled Zn|PNF-6|VO full cell demonstrates superior cycle stability, retaining a capacity retention of 80 % over 4000 cycles at 5 A g. This work pioneers a scalable route toward high-performance hydrogel-enhanced paper separators, addressing critical challenges for ZIBs industrialization.