Biomass derived ultrathin nanofiber separator for regulating homogeneous Zn2+ flux and achieving dendrite-free aqueous zinc-ion batteries

The practical application of aqueous zinc (Zn)-ion batteries (AZIBs) is significantly hindered by the non-uniform deposition of Zn and the associated dendrite growth. In this study, a cost-effective, lightweight, and mechanically robust Xuan paper (XP), as a traditional biomass material, is employed as an ultrathin nanofiber separator for AZIBs. Composed of cellulose and hemicellulose, the nanofibers in XP are rich in polar -OH groups and abundant pores, which can effectively regulate Zn²⁺ flux and promote uniform Zn deposition. This regulation contributes to enhanced electrochemical performance of the AZIBs. As a result, Zn symmetric cells equipped with the XP separator exhibit long-term cycling stability of up to 4000 h at 0.2 mA cm⁻² and 0.2 mAh cm⁻², which significantly outperforming cells using conventional glass fiber separators. Moreover, the Zn|XP|V₂O₅ full cell delivers a high specific capacity of 168 mAh g⁻¹ and outstanding cycling durability, retaining 89.7 % of its capacity after 1400 cycles at 1 A g⁻¹. This study presents a simple and effective strategy for designing XP derived ultrathin nanofiber separators with high ionic conductivity and functional regulation capability, offering a promising approach to controlling Zn deposition and enabling the development of high-performance AZIBs.