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

TL;DR

This study shows how controlling the shape of a material in a gel improves the performance and lifespan of aqueous zinc-ion batteries.

Contribution

A gel-based strategy is introduced to control the morphology of UiO-66 in separators, enhancing battery performance.

Findings

Octahedral UiO-66 in CNF gels improves zinc ion migration and suppresses dendrite growth.

The separator achieves 800 hours of cycle life in symmetric cells and 98.1% capacity retention in full cells.

The gel architecture forms uniform ion transport channels and enhances hydrophilicity and porosity.

Abstract

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.

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