Synergistic Regulation of Water Activity and Ion Transport by an In Situ-Grown MOF/Bacterial Cellulose Separator for High-Performance Zn Anodes.

Aqueous zinc-ion batteries (AZIBs) are promising for grid-scale energy storage but suffer from dendritic growth and water-induced side reactions on Zn anodes. Separator design critically regulates the electrode-electrolyte interface, yet conventional approaches often struggle to simultaneously achieve mechanical robustness, efficient ion transport, and effective water activity regulation. Herein, we design a hybrid bacterial cellulose@UiO-66-NH2 (BM) separator via in situ growth of UiO-66-NH2 within a bacterial cellulose (BC) hydrogel, followed by a final hot-pressing step, which synergistically combines the complementary properties of both components. The BC matrix confines water via hydrogen bonding, suppressing parasitic reactions, while the amino-functionalized MOF opens up ion-transport pathways that sieve and desolvate Zn2 + for uniform flux. This design yields a thin (∼34 µm thick), robust (161.71 MPa tensile strength), highly porous (71.6%), and ionically conductive (3.53 mS cm-1) membrane. Consequently, the BM separator enables a stable Zn anode with a long cycling life of over 1000 h at 2 mA cm-2/2 mAh cm-2 in symmetric cells and significantly improved performance in Zn||NH4V4O10 full cells, retaining 85.32% capacity after 500 cycles at 1 A g-1. This work presents a strategy integrating mechanical robustness with dual regulation of water state and ion transport for high-performance AZIBs.