Chelating Additive Regulating Zn‐Ion Solvation Chemistry for Highly Efficient Aqueous Zinc‐Metal Battery

Abstract Aqueous zinc‐metal batteries (AZMBs) usually suffered from poor reversibility and limited lifespan because of serious water induced side‐reactions, hydrogen evolution reactions (HER) and rampant zinc (Zn) dendrite growth. Reducing the content of water molecules within Zn‐ion solvation sheaths can effectively suppress those inherent defects of AZMBs. In this work, we originally discovered that the two carbonyl groups of N‐Acetyl‐ϵ‐caprolactam (N‐ac) chelating ligand can serve as dual solvation sites to coordinate with Zn2+, thereby minimizing water molecules within Zn‐ion solvation sheaths, and greatly inhibit water‐induced side‐reactions and HER. Moreover, the N‐ac chelating additive can form a unique physical barrier interface on Zn surface, preventing the harmful contacting with water. In addition, the preferential adsorption of N‐ac on Zn (002) facets can promote highly reversible and dendrite‐free Zn2+ deposition. As a result, Zn//Cu half‐cell within N‐ac added electrolyte delivered ultra‐high 99.89 % Coulombic efficiency during 8000 cycles. Zn//Zn symmetric cells also demonstrated unprecedented long life of more than 9800 hours (over one year). Aqueous Zn//ZnV6O16 ⋅ 8H2O (Zn//ZVO) full‐cell preserved 78 % capacity even after ultra‐long 2000 cycles. A more practical pouch‐cell was also obtained (90.2 % capacity after 100 cycles). This method offers a promising strategy for accelerating the development of highly efficient AZMBs.