A bioinspired flexible hydrogel electrolyte with β-sheet–directed interphase for dendrite-free Zn metal batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) have attracted growing attention due to their intrinsic safety, low cost, and environmental compatibility. However, challenges such as zinc dendrite formation, electrode passivation, and parasitic side reactions continue to impede long-term cycling stability. Inspired by conformational transitions in natural proteins, we propose a biomimetic interfacial engineering strategy by introducing silk fibroin (SF) into a hydrogel electrolyte. Upon solvent induction, SF undergoes a structural transition from α-helix to β-sheet, forming a dense, ionically conductive interphase on the Zn anode. The ordered β-sheet network, enriched with Zn-affinitive polar groups, modulates Zn²⁺ solvation, guides deposition along the (002) crystal plane, and suppresses dendrite growth and side reactions. Density functional theory (DFT) and molecular dynamics (MD) simulations reveal the mechanism of solvation structure reconstruction and interfacial stabilization. Benefiting from this design, the β-SF hydrogel electrolyte enables stable Zn plating/stripping over 2500 hours at 1 mA cm⁻², while the Zn//MnO₂ full cell retains 93.8 % capacity after 1500 cycles at 1.0 A g⁻¹. Moreover, the fibrous and flexible configuration exhibits excellent mechanical durability and device compatibility. This work presents a protein-based interfacial strategy driven by conformational regulation, offering a new pathway toward high-performance, durable, and flexible AZIBs.