Wood Cellulosic Membrane With Abundant Nanochannels for Stabilizing Aqueous Zn‐Ion Batteries

ABSTRACT The practical deployment of aqueous Zn‐ion batteries (AZIBs) is severely hindered by uncontrolled zinc dendrite growth and parasitic side reactions at the anode–electrolyte interface. As a critical component, the separator governs Zn 2+ transport and interfacial stability, yet conventional glass fiber separators suffer from low mechanical strength and disordered porous structures, causing uneven ion flux, side reactions, and dendrite growth. Herein, a wood‐derived cellulosic membrane with abundant nanochannels and water‐binding functionalities is developed as a sustainable, low‐cost separator. The densely aligned cellulose nanofibrils impart exceptional mechanical robustness, while hydroxyl‐rich surfaces form strong hydrogen bonds with water molecules, immobilizing free water and stabilizing the electrolyte–anode interface. Moreover, the hierarchical fibrillar network, swollen by electrolyte uptake, forms well‐aligned nanochannels that enable uniform Zn 2+ flux and homogenize electric field distribution, thereby mitigating tip‐induced dendrite propagation. As a result, Zn||Zn symmetric cells show ultra‐stable cycling for 1920 h, Zn||Cu cells deliver a high average Coulombic efficiency of 99.5% over 1000 cycles, and Zn||MnO 2 full cells retain 88.8% capacity after 1000 cycles at 1 A g −1 . This work highlights the potential of ordered wood cellulose membranes as sustainable and low‐cost separators for dendrite‐free, high‐performance AZIBs.