A Green andOrganic Solvent-Free Strategy for ConstructingCNF Coatings Enabling Highly Stable Zn Metal Anodes

Abstract Among strategies for protecting anodes in aqueous Zn-ion batteries (AZIBs), the slurry coating method is widely used to construct protective layers. However, conventional slurry coating processes often inevitably employ organic solvents, which contradicts the inherently environmentally friendly nature of AZIBs. This study proposes a “hydrophilic substrate modification–aqueous dispersion spraying” strategy for protective layer construction: a hydrophilic Zn foil (H–Zn) was prepared through a UV/O3 cleaning process, and carboxylated cellulose nanofibers (CNF) were spray-coated onto the H–Zn substrate using ultrapure water as the sole dispersion medium, successfully fabricating an H–Zn@CNF anode. The entire process was conducted without any organic solvents, offering distinct eco-friendly advantages. Symmetrical cell tests demonstrated excellent cycling stability of the H–Zn@CNF anode: it achieved stable cycling for 2500 h (vs bare Zn, 184 h) at 1 mA cm–2/1 mAh cm–2 and for 1250 h (vs bare Zn, 50 h) at 2 mA cm–2/1 mAh cm–2. The enhanced stability originates from the dual functions of the CNF protective layer: first, it isolates the Zn substrate from active water molecules in the electrolyte, suppressing hydrogen evolution reactions and the formation/accumulation of byproducts; second, the carboxyl groups on CNF molecular chains promote the desolvation of [Zn(H2O)6]2+, facilitating rapid and uniform deposition of Zn2+ and thereby inhibiting Zn dendrite growth. This study achieves a green preparation route for highly stable AZIB anodes and provides a novel approach for promoting the environmentally friendly fabrication and industrial application of aqueous batteries.