Scalable and sustainable sulfonated cellulose separators toward practical Ah-level aqueous batteries

Aqueous zinc-ion batteries have emerged as a promising complement to lithium-ion batteries due to inherent safety benefits. However, challenges such as detrimental side reactions, Zn dendrites formation, high manufacturing cost, and limit capacity amplification hinder their broader adoption. Herein, we introduce a scalable and cost-effective sulfonated cellulose separator derived from eco-friendly and highly hydrophilic bacterial cellulose for aqueous batteries. The sulfonated separator features a thickness of 50 μm, presents a high tensile strength of 167 MPa, and an ionic conductivity of 13.1 mS cm⁻¹. Both experimental results and theoretical simulations demonstrate that the incorporation of sulfonate groups into the cellulose matrix effectively suppresses sulfate ion migration while enhancing zinc ion transport. These properties ensure uniform zinc ion flux and preventing dendrite formation. In practical applications, a 1.2 Ah pouch cell using the sulfonated separator with a high cathode mass loading of 21.6 mg cm⁻² was achieved, highlighting the potential of this sulfonated separator for scalable, durable and high-capacity aqueous batteries.