Multifunctional electrolyte additives enabled adaptable interface toward stabilizing Zn metal anodes

Abstract

H₂ evolution, Zn dendrites formation, and side reactions have severely hindered the practical applications of aqueous zinc-ion batteries. Herein, a multifunctional leucine additive is introduced into ZnSO₄ electrolyte to create adaptable interfaces. The polar groups make leucine preferentially adsorb on Zn metal surface, inducing Zn²⁺ uniform deposition to suppress Zn dendrites growth, while the hydrophobic groups prevent Zn metal contacting from water, inhibiting water-related side reactions. Meanwhile, the zwitterionic amino and carboxyl segments can dynamically adjust the pH changes with a stable interfacial microenvironment, thereby inhibiting side reactions. Besides, the high affinity of leucine to Zn²⁺ regulated the solvated structure and facilitated forming inorganic ZnS layer on Zn metal, reducing the Zn-ions desolvation energy barrier and enhancing Zn-ions plating kinetics. As a proof of concept, the symmetric cells with leucine additives exhibit an extended cycling lifetime of 2700 h at 1.0 mA cm⁻²/1.0 mAh cm⁻² when compared to bare ZnSO₄ electrolyte (200 h). Moreover, the full cells pairing with VO₂ cathodes displayed superior long-term cycling stability with 91 % capacity retention after 1800 cycles, which can work as flexible energy storage systems to power electronic watch.