Durable Aqueous Zinc-Ion Batteries via Weak Solvation-Induced Anion-Derived Interphases

The practical application of environmentally friendly aqueous Zn-ion batteries is hindered by notorious side reactions and uncontrolled dendrite growth, which compromise resource efficiency and device longevity. While anion-derived solid electrolyte interphase (SEI) layers offer promise in enhancing reversibility, achieving anion enrichment at the anode interface requires precise design of Zn²⁺ solvation structures. This study leverages the weak solvation effects of niacinamide (Nam) to reconfigure Zn²⁺ solvation structures in hydrated eutectic electrolytes (HEEs). Electrochemical and spectroscopic analyses confirm that these coordinated anions enhance Zn²⁺ desolvation kinetics and preferentially decompose to form a robust inorganic/organic hybrid SEI layer on the Zn anode. Furthermore, the inherent wettability of Nam facilitates preferential adsorption on the Zn anode while disrupting free water networks and suppressing water-induced side reactions. The unique hybrid SEI layer enables improved reversibility of the Zn anode with 99.1% Coulombic efficiency along with smooth Zn deposition. As a result, the corresponding Zn//polyaniline (PANI) full cell delivers excellent capacity retention of 83% after 3000 cycles at 1.0 A g^–1. This study provides deep insight into constructing anion-derived SEI layers through the weak solvation effect and offers practical strategies for designing advanced aqueous electrolytes.