A three-functional zwitterionic arginine electrolyte additive for modified zinc anodes

Abstract

The uncontrolled formation of zinc dendrites and concomitant parasitic reactions at the interface critically undermine the reversibility and operational stability of aqueous zinc electrodes. In this study, a zwitterionic compound, C₆H₁₄N₄O₂, was introduced as an electrolyte additive designed to simultaneously modulate the solvation sheath of Zn²⁺ ions, engineer the electrode/electrolyte interfacial double-layer structure, and facilitate the in situ formation of a robust, ion-conductive solid electrolyte interphase (SEI) layer on the zinc anode. Consequently, the additive effectively suppresses zinc dendrite growth and mitigates parasitic hydrogen evolution. C₆H₁₄N₄O₂ preferentially adsorbs onto the active sites associated with zinc corrosion and hydrogen evolution, thereby effectively inhibiting these side reactions. Furthermore, the adsorbed C₆H₁₄N₄O₂ redistributes the Zn²⁺ ion flux, facilitates the desolvation of [Zn(H₂O)₆]²⁺, and promotes uniform zinc deposition at low overpotentials. Consequently, long-term cycling stability with minimal voltage hysteresis (>2900 h at 1 mA cm⁻² and 1 mAh cm⁻²) was achieved in Zn∥Zn symmetric cells. When paired with a polyaniline (PANI) cathode, the assembled PANI∥Zn battery with the addition of C₆H₁₄N₄O₂ exhibited a capacity of 142.83 mAh g⁻¹ after 1500 cycles, achieving a capacity retention rate of 85.9%. In contrast, the Zn∥PANI full cell using the pure ZnSO₄ electrolyte demonstrated a capacity of 95.14 mAh g⁻¹ and a capacity retention rate of 77.9%. These results highlight the environmental friendliness of C₆H₁₄N₄O₂ as an ideal electrolyte additive in aqueous zinc-ion batteries.