Bifunctional Keratin Enables Highly Stable Zinc Anodes via Interfacial Nucleation Regulation

Currently, various protein molecules are being applied to aqueous zinc-ion batteries to enhance their cycle life. However, traditional proteins exhibit limited functionality, and due to their low content of zinc-affinity groups, they struggle to form uniform and stable solid electrolyte interlayers. In this study, sulfonated modified keratin (SBKP) with enhanced zinc affinity was obtained through SBMA modification. SBKP self-assembles into a SEI layer on the zinc foil surface. The sulfonic acid groups (─SO₃ ^{2 -}) in SBKP effectively regulate interfacial charge transfer through strong Lewis acid-base interactions, enhancing nucleation driving forces and promoting rapid, uniform Zn^{2 +} deposition. Furthermore, SBKP reconstructs the hydrogen-bond network in the outer solvated shell layer, achieving a favorable balance between ion transport kinetics and corrosion resistance. Leveraging these properties, the SBKP@Zn symmetric cell demonstrates an exceptionally long cycle life of 3281 h at a current density of 1 mA cm^{- 2}. In a full-cell configuration with a MnO₂ cathode, stable cycling performance is maintained even after 1000 cycles. This study proposes a scalable and effective interfacial engineering strategy for stabilizing zinc anodes, offering valuable insights for developing long-lasting, high-performance aqueous micro-energy storage systems suitable for flexible electronic devices.