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

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 ZnSO4-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 -NH2) suppresses the side reactions. Namely, silk peptide regulates the solvation structure of Zn2+ to decrease coordinated active H2O and SO42-, and tends to anchor on Zn anode surface for the isolation of contact H2O/SO42- 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 ZnSO4 electrolyte with only 5 mg mL(-1) of silk peptide (approximate to 0.49 USD L-1), promising practical applications of reversible zinc-ion batteries.