Boosting the practical applications of zinc-ion batteries via zwitterion-mediated solvation and interfacial chemistry

Abstract

The thermodynamic instability of Zn anodes in aqueous electrolytes, driven by corrosion and hydrogen evolution reactions, severely restricts the practical applications of aqueous zinc-ion batteries. Herein, a zwitterion-mediated solvation chemical and interfacial engineering strategy is proposed to address these challenges. By introducing aniline blue (AB) with (–SO₃H) and amine (–NH₂) groups as a multifunctional electrolyte additive, the interfacial pH fluctuations are dynamically stabilized, together with the reconstructed electrode/electrolyte interface and Zn²⁺ solvation structure. Real-time measurements show that the AB enables in situ pH-buffering during both shelving and working time, suppressing parasitic hydrogen evolution and the self-corrosion of Zn. The parasitic reactions are further inhibited by the preferential absorption of AB at the Zn surface, which reshapes the electrical double layer, creating a water-deficient micro-environment at the Zn/electrolyte interface and homogenizing Zn²⁺ deposition. Simultaneously, AB participates in the solvation structure, resulting in fast electrochemical kinetics. This strategy enables the Zn‖Zn cells with over 1600 h calendar aging time, high reversibility and robust stability under harsh conditions (a 220 h durable time even under 80% depth of discharge, DoD). Specifically, the Zn‖V₂O₅ full cells retain a high capacity of 105 mAh g⁻¹ after 3000 cycles at 5000 mA g⁻¹. Even at an ultralow negative to positive (N/P) ratio of 2.0, the full cells can still deliver a high capacity of 153 mAh g⁻¹ after 120 cycles.