Ultrasound-Induced Microstructural Fusion of UiO-66-NH2 for Advanced Cellulose Nanofiber Composite Separators toward Ultra-stable Zinc-Ion Batteries

Abstract

Achieving uniform zinc deposition is crucial for high-performance aqueous zinc-ion batteries, yet it remains a significant challenge. While functional separators based on metal–organic frameworks (MOFs) like UiO-66-NH2 offer a promising route to regulate ion flux, their effectiveness is often hampered by the energy-intensive synthesis of MOFs and their poor dispersion within polymer matrices. Herein, we report a rapid, room-temperature ultrasound-assisted synthesis that yields UiO-66-NH2 with a unique surface-fused morphology and a hierarchical pore system within just 1 h. Unlike its conventional counterpart with a well-defined octahedral shape, this ultrasound-induced MOF (U-UN) forms a homogeneous and tightly integrated composite with cellulose nanofibers, constructing a separator with optimized ion-transport channels and interfacial stability. The U-UN-based separator demonstrates superior ionic conductivity and Zn2+ transference number, effectively guiding the preferential growth of Zn along the (002) plane. Consequently, a Zn||Zn symmetric cell equipped with this separator achieves an ultrastable cycling life exceeding 1180 h, and a Zn||MnO2 full cell retains nearly 100% capacity after 600 cycles at 1 A g–1. This work not only presents a green and efficient synthesis strategy for advanced MOFs but also provides fundamental insights into the design of functional separators through microstructure engineering for long-lasting metal batteries.