Coaxial Wet-Spinning Fiber-Shaped Zn-Ion Batteries Enabled by Zn Powder and Cellulose Nanofiber Reinforced Gel Electrolyte

Abstract

Flexible zinc-ion batteries (FZIBs) hold great promise for wearable electronics but face challenges from dendrite growth and interfacial failure under mechanical deformation. Here, we propose a coaxial wet-spinning strategy to synergistically integrate a high-strength polyvinyl alcohol/carboxylated cellulose nanofiber (PVA/CNFs) gel electrolyte with a zinc powder/polyethylene oxide-polyethylene glycol/carbon nanotube (Zn/PEO-PEG/CNT) composite anode. The PVA/CNFs gel electrolyte exhibits exceptional mechanical flexibility (800% strain, 11 MPa strength) and high ionic conductivity (33.1 mS cm-1), enabled by dynamic hydrogen bond networks. Meanwhile, the Zn/PEO-PEG/CNT composite anode facilitates uniform Zn2+ deposition through a three-dimensional conductive network and interfacial corrosion inhibition. The coaxial architecture ensures intimate electrode/electrolyte contact, achieving a Zn||Zn symmetric cell lifespan exceeding 1600 h at 1 mA cm-2 and a Zn||VO2 full cell that retains a capacity of 177 mAh g-1 after 1000 cycles at 2 A g-1. Finite element simulations and in situ microscopy reveal that the hierarchical design homogenizes electric field distribution and guides Zn2+ planar deposition along (002) crystal facets. This work provides a scalable interfacial engineering paradigm for mechanically durable and dendrite-free flexible energy storage devices.