Green and Mass-Producible Biomass Separator with Nanoconfined Channels for Practical High-Performance Zinc-Ion Batteries

Aqueous zinc-ion batteries hold significant importance in energy storage realms, yet the prevailing glass fiber (GF) separators suffer from high cost, excessive thickness, and poor mechanical property, which pose formidable challenges for widespread adoption. Herein, we propose a paradigm shift from a remedial to preventive design by engineering a truly scalable, low-cost, and eco-friendly separator. By hydrogelling sodium alginate (SA) on commercial weighing paper (WP) and in situ forming an “egg–box” structure, we construct a nanoconfined zinc alginate hydrogel-modified separator (ZAH–WP), whose cost is only 0.45% of the GF separator (USD $1.10 m –2 vs USD $244 m –2 ). Furthermore, the ZAH–WP separator reduces thickness from ∼841 μm (GF) to ∼188 μm and enhances mechanical strength to 51.62 MPa, 129 times that of the GF separator (∼0.40 MPa). Encouragingly, the Zn||ZAH–WP||Zn cell delivers stable cycling over 2510 h, and the Zn||ZAH–WP||Cu cell achieves an average coulombic efficiency of 99.50%, which outperforms the GF separator in overall electrochemical performance.