High-entropy solvation chemistry towards affordable and practical Ah-level zinc metal battery.

Abstract

Aqueous zinc-ion batteries offer sustainable large-scale storage potential with inherent safety and low cost, yet suffer from limited energy density and cycle life due to aqueous electrolyte constraints. Here, we introduce affordable, stable electrolyte (0.33 $·kg^-1) incorporating minimal multi-halogen anions (Cl^-, Br^-, and I^-) to create a high-entropy solvation structure enabling high-performance zinc batteries. Despite the small amount, the diversified mono-halogenated contact ion pair and multi-halogenated aggregate solvation structures create the unique high-entropy solvation structure, to form the lean-water halogenated interfacial environment, suppressing the hydrogen evolution reaction, while facilitating cascade desolvation. Multi-halogen additives generate diverse contact ion pairs (Zn-X, X = Cl/Br/I) with compact solvation shells accelerating ion transport. In this way, the high-entropy solvation structure breaks the trade-off between plating overpotential (energy efficiency) and plating/stripping reversibility (Coulombic efficiency). As a result, the high-entropy solvation-based electrolyte enables practical zinc metal battery with 152.2 Wh kg^-¹_electrode for 120 cycles at lean electrolyte of 2.4 μL mg^-¹ and an Ah-level pouch cell is validated with high Coulombic efficiency of over 99.90% for over 250 cycles. Our findings emphasize the importance of electrolyte design for the precise control of anion-cation interactions for stable Zn/electrolyte interface and enable practical zinc metal battery with high energy and low cost.