Electrolyte and Interfacial Strategies for Enhanced Kinetic Performance in Zinc Metal Batteries by Deep Eutectic Effects  

Zinc-based batteries (ZMBs) have been thrust into the spotlight once more, being particularly appealing for large-scale energy storage due to their abundant availability, eco-friendliness, and inherent safety. Unlike other metals like lithium, sodium, or potassium, zinc isn't easily affected by elements such as oxygen or moisture. This trait not only makes a wider variety of electrolytes available but also cuts down on the associated costs. Yet, challenges like the formation of dendritic structures and undesired reactions at the zinc-electrolyte juncture limit the potential of ZMBs. Recently, there's been a shift towards using deep eutectic solvents (DES) as a substitute for the typical aqueous electrolytes by uniquely combining zinc salts with neutral ligands. This pairing reduces the connection between zinc ions and water, fostering stronger hydrogen bonds between water and the eutectic materials. A key factor here is the tight bond between zinc ions and ligands, which raises the desolvation energy of zinc ions, ensuring a more uniform zinc deposition. Building on this foundational knowledge, researchers are keen on exploring ligands with varied molecular characteristics to balance the relationship among zinc ions, water, and eutectic elements. Such an approach is seen as a potential game-changer in enhancing the durability and performance of the zinc anode. Furthermore, the concept of the Solid Electrolyte Interphase (SEI) brings a novel solution to the table, aiming to overcome inherent challenges linked to zinc anodes. One way to achieve this is by altering the solvation structure in DESs, paving the way for modifying the reduction potentials of the electrolyte's components. This modification can be pivotal in creating an optimal SEI layer. Such advancements can unlock enhanced functionalities, notably in stymieing dendrite growth and promoting consistent, efficient performance for ZMBs. In this project, we propose the development of linear amide-based deep eutectic electrolytes with cyclic amide additives, a strategic approach intended to regulate the solvation structure while limiting water activity, thus promoting smooth and stable Zn deposition. Moreover, we plan to incorporate electrolyte diluents to attain DES electrolytes with higher ion conductivity and limited water activity. In addition, the F-rich species as additives in DES electrolytes will be explored meticulously, which is designed to establish high-fluoride content SEI with enhanced ionic conductivity. Benefiting from the highly reversible and stable zinc interface, efforts will be dedicated to the development of ampere-hour (Ah) level high-voltage, high-capacity, long-cycle zinc metal full batteries utilizing the developed DES electrolytes.