Regulating Zn2+ solvation structure in eutectic electrolytes for rechargeable zinc batteries

Rechargeable zinc batteries (RZBs) are promising candidates for large-scale energy storage due to their intrinsic advantages of affordability, inherent safety, and environmentally friendly properties. Despite numerous works focused on electrode materials, non-electrode components, particularly electrolytes, are crucial in attaining high energy and power density in RZBs. Optimal electrolytes should be equipped with excellent compatibility with electrode materials, high safety, and long-term durability. Eutectic electrolytes, a novel class of electrolytes, are widely studied because of their non-flammability, structural flexibility, thermal and chemical stability, ease of fabrication, and high tunability. Although some reviews have summarized their application in electrochemical energy storage, further development requires in-depth analysis. This review aims to provide a mechanistic understanding of eutectic electrolytes and an overview of their recent advancements in RZBs. We classify eutectic electrolytes into four categories according to the formation mechanisms and depict the relations between the structure and thermodynamic-transport-electrochemical properties of eutectic electrolytes. Additionally, we summarize recent progress and applications of the four typical eutectic electrolytes in RZBs, specifically focusing on how various compositions affect the solvation structure. We also discuss the remaining challenges and potential future perspectives of eutectic electrolytes, which deliver appealing opportunities and prospects for practical RZB systems.