Blocking the passivation reaction via localized acidification and cation selective interface towards highly stable zinc anode

Abstract

The variations of pH triggers either the formation of zinc sulfate hydroxide (ZSH) or the hydrogen evolution reaction (HER), leading to unsatisfactory zinc anode efficiency. In order to establish a balanced approach that suppresses the HER while creating an acidic environment to eliminate ZSH formation, this study introduces an environmentally friendly chelating additive, tetrasodium iminodisuccinate (IDS), into the ZnSO4 electrolyte. This additive serves to generate a localized acidic environment and a cation-selective surface barrier. The preferentially adsorbed IDS anions create a water-poor interface and engage in synergistic regulation of cation and anion via electrostatic effects, promoting smooth Zn deposition and reducing by-product formation. Additionally, IDS can strongly interact with Zn2+ and adapt to pH variations, thereby providing a stable environment that mitigates side reactions. Unlike sacrificial additives, IDS demonstrates stability under test conditions, resulting in a truly reversible and stable electrolyte system. The implementation of this multifunctional additive results in a prolonged lifespan of metallic Zn, reaching 2548 h, and a promoted coulombic efficiency of 99.5 %. Furthermore, the improved stability of Zn anodes is observed in Zn//LiFePO4 cells, exhibiting the capacity retention of 97.0 % over 800 cycles. This strategy opens up a new pathway for enhancing the stability and reversibility of Zn anodes.