Multispecies interfacial regulation via keratin-engineered separators for dendrite-free aqueous zinc metal anodes

Aqueous zinc-ion batteries hold great promise for stationary energy storage and personal electronics, yet their practical application is hindered by uncontrolled Zn dendrite growth and parasitic reactions. Herein, a sustainable keratin-functionalized glass-fiber separator (GF@WK) is developed by upcycling waste wool to simultaneously reinforce structural integrity and regulate interfacial ion transport. Structurally, the interconnected keratin network refines the separator's pore structures and significantly enhances mechanical robustness. As an added reliability feature for emergency power applications, this coating provides intrinsic heat resistance by undergoing self-sacrificial carbonization under thermal abuse to mitigate separator shrinkage. Concurrently at the molecular level, benefiting from sequence-encoded polar functionalities, keratin coordinates Zn 2+ , disrupts the [Zn(H 2 O) 6 ] 2+ hydration shell, and electrostatically confines SO 4 2- anions. This promotes Zn 2+ desolvation, suppresses side reactions, and homogenizes ion flux for uniform, dendrite-free Zn deposition. Consequently, the Zn//Cu half-cell achieves an average Coulombic efficiency of 99.5% over 300 cycles, and the Zn//Zn symmetric cell cycles stably for over 3000 h. The Zn//Na 2 V 6 O 16 ·3 H 2 O full cell delivers 151 mAh g −1 at 5 A g −1 with 90.1% capacity retention after 2000 cycles. Finally, pouch cells demonstrate reliable power delivery under extreme conditions, highlighting a sustainable biomolecular interface engineering strategy for high-performance aqueous metal battery chemistry and beyond.