Synergistic Solvation and Interface Regulations of Eco‐Friendly Silk Peptide Additive Enabling Stable Aqueous Zinc‐Ion Batteries

Abstract Aqueous Zn‐ion batteries have aroused much attention recently, yet challenges still exist in the lack of low‐cost, highly stable electrolytes to tackle the serious side reactions at Zn anode–electrolyte interface. Herein, a ZnSO 4 ‐based low‐cost aqueous electrolyte is demonstrated with a small amount of eco‐friendly silk peptide as an efficient additive. Compared with silk sericin and fibroin, silk peptide with abundant strong polar groups (COOH and NH 2 ) suppresses the side reactions. Namely, silk peptide regulates the solvation structure of Zn 2+ to decrease coordinated active H 2 O and SO 4 2− , and tends to anchor on Zn anode surface for the isolation of contact H 2 O/SO 4 2− as well as electrostatic shielding, demonstrating synergistic solvation and interface regulating effect. Consequently, the excellent cycle life (3000 h) and Coulombic efficiency (99.7%) of Zn anodes are revealed in 2 m ZnSO 4 electrolyte with only 5 mg mL −1 of silk peptide (≈0.49 USD L −1 ), promising practical applications of reversible zinc‐ion batteries.