Solvation and interfacial chemistry in ionic liquid based electrolytes toward rechargeable lithium-metal batteries

Abstract

Rechargeable lithium metal batteries (LMBs) are a highly promising technology for high-energy-density storage systems due to the low electrochemical potential and high theoretical capacity of the lithium metal anode. The electrolyte plays a pivotal role among the critical components of LMBs. However, traditional organic electrolytes pose significant safety risks and shorten the battery life due to their electrochemical instability, volatility, and flammability. Alternatively, ionic liquids (ILs), composed of anions and cations, are room-temperature molten salts characterized by ultra-low volatility, high ionic conductivity, excellent thermal stability, low flammability, and wide electrochemical windows. Based on these properties, liquid IL electrolytes (ILEs) and polymeric IL electrolytes (PILEs) have shown immense potential in enhancing battery cycle stability, energy density, lifespan, and safety. This review aims to comprehensively explore and summarize recent applications of ILEs and PILEs in LMBs, including their use as liquid and solid-state electrolytes, as well as ILs serving as film-forming additives, interfacial wetting agents, and pretreatment reagents. Additionally, the review delves into the solvation structures of Li⁺ ions within different IL-based electrolytes and the resulting interfacial chemical characteristics. Finally, based on literature reports and our previous work, we identify current challenges and propose solutions for the future application of IL-based electrolytes in LMBs.