Impact of Gel-Derived Morphology-Controlled UiO-66/Cellulose Nanofiber Composite Separators on the Performance of Aqueous Zinc-Ion Batteries

Zinc dendrite growth and side reactions remain critical challenges hindering the advancement of aqueous zinc-ion batteries (AZIBs). This study proposes a gel-based strategy for designing high-performance separators by regulating the crystal morphology of the metal-organic framework UiO-66 within a cellulose nanofiber (CNF) gel matrix. The resulting gel-derived separators exhibit distinctive structural and interfacial properties that significantly enhance battery performance. Compared with hierarchical porous structures (H-UiO-66), the octahedral morphology (O-UiO-66) disperses more uniformly in the CNF gel network, forming well-defined ion transport channels through its integrated gel architecture. The fabricated O-UiO-66/CNF gel separator demonstrates exceptional hydrophilicity (contact angle 21°), high porosity (73.2%), and significantly improved zinc ion migration number (0.72). Electrochemical tests reveal that this gel-based separator effectively guides uniform zinc deposition while suppressing dendrite growth. Zn/Zn symmetric cells using the O-UiO-66/CNF gel separator achieve a cycle life exceeding 800 h at 1 mA cm^-2. The Zn/MnO₂ full cell maintains 98.1% capacity retention after 100 cycles at 1 A g^-1. This work establishes a structure-performance relationship between MOF morphology and gel separator properties, providing new insights for designing advanced gel-based materials for AZIBs.