3D Interconnected Zn‐Ion Pathways Through Anionic Nanochannels Surrounding Bacterial Cellulose Nanofibers by Repetitive Interfacial Assembly for Aqueous Zn‐Ion Battery Separators

ABSTRACT Conventional glass fiber (GF) separators have large pores with a wide size distribution, which exacerbate dendrite formation in aqueous Zn‐ion batteries via irregular ionic flux. Herein, a repetitive interfacial assembly (RIA) method is introduced to prepare a hydrogel separator with interconnected anionic nanochannels (ANCs) surrounding the 3D network of bacterial cellulose (BC) nanofibers. This enables conformal coating of the BC nanofibers with nanometer‐thick, carboxylate (─COO − )‐rich polymeric layers via bottom‐up assembly and growth. The optimal sample exhibits an ionic conductivity of 40.4 mS cm −1 and a high Zn 2+ transference number of 0.75, which is attributed to the rapid migration of partially desolvated Zn ions via transient coordination with ─COO − in the ANCs. Furthermore, the homogeneous ion flux from the nanostructured RIA hydrogel and the decreased desolvation energy of the less hydrated Zn ions synergistically improve the charge transfer at the Zn‐metal electrode, thereby resulting in smooth and planar Zn deposition and dendrite suppression. Compared to the bare BC and GF, the RIA‐based Zn//Zn symmetric cell operates stably for 1000 h at 5 mA cm −2 and 1 mA h cm −2 , and the Zn//NaV 3 O 8 ·1.5H 2 O full cell exhibits superior cycling stability and rate capability.