Modulating the interfacial microenvironment via zwitterionic additive for long-cycling aqueous Zn-ion batteries

Aqueous zinc-ion batteries (AZIBs) have garnered extensive attention as promising energy storage systems because of the advantages of low cost and high safety. However, severe parasitic reactions at the Zn anode surface pose a huge challenge for the practical application of AZIBs, especially the intricate hydrogen evolution reaction (HER) and Zn dendrite growth. Herein, zwitterionic taurine with isoelectric point property is introduced as an electrolyte additive to construct a passivation layer by adapting its net charge to the microenvironment variation for stabilizing the Zn anode. The experimental and theoretical results reveal that taurine can not only in-situ form a hydrophobic and zincophilic layer on the Zn anode surface via the chelation with Zn²⁺ in the alkaline interfacial microenvironment, but also buffer the pH change dynamically, thus effectively suppressing the HER and Zn dendrite growth. As a consequence, the taurine-containing electrolyte enables a stable cycling of Zn anodes in symmetric Zn∥Zn cells for more than 1800 h under a deep plating/stripping condition (5 mA cm⁻² and 5 mAh cm⁻²). More encouragingly, the full cells coupled with the NH₄V₄O₁₀ cathode can also exhibit an excellent capacity retention of 89.8% after 1200 cycles. This efficient strategy with an environmental adaptive additive offers valuable insights for mitigating the side reactions to achieve practical AZIBs and beyond.