A gradient pore structure cellulose-based separator with halloysite nanotubes to regulate ion transport for ultra-stable dendritic Zn anodes

Aqueous zinc-ion batteries (AZIBs) are expected to be used for large-scale energy storage due to their low cost and safety, but uncontrolled Zn deposition can lead to dendrite growth. To solve this problem, we designed a cellulose-based fiber-reinforced separator (PCH-x@CF) to achieve a gradient pore structure by non-solvent-induced phase separation (NIPS) method, thereby improving the electrolyte permeation, ion transport, and ionic conductivity of the separator. The separator regulates Zn deposition through both physical and chemical mechanisms, inhibiting hydrogen evolution (HER) and dendrite formation. The key to its performance is the addition of halloysite nanotubes (HNTs), which improve hydrophilicity, thermal stability (326.6 °C), and Zn 2+ flux uniformity. Molecular dynamics (MD) simulations show that the negatively charged Si–O - group in HNTs can replace the solvated H 2 O in the Zn 2+ coordination shell, thereby reducing the Zn 2+ desolvation energy barrier. In addition, the functional groups (-CN, –OH) in the PCH-x@CF matrix form Zn–O and Zn–N bonds, further promoting uniform Zn 2+ transport. In electrochemical tests, the PCH-12@CF separator was stable for 2500 h at 0.1 mA cm −2 and maintained up to 87.5 % capacity after 2000 cycles at 1.0 A g −1 . This work provides an advanced design strategy for high-performance AZIBs separators by combining gradient pore structures with target chemical functional groups.