Locally Concentrated Ionic Liquid Electrolytes for Lithium-Metal Batteries

Non-flammable ionic liquid electrolytes (ILEs) are well-known candidates for safer and long-lifespan lithium metal batteries (LMBs). However, the high viscosity and insufficient Li+ transport limit their practical application. Recently, non-solvating and low-viscosity co-solvents diluting ILEs without affecting the local Li+ solvation structure are employed to solve these problems. The diluted electrolytes, i.e., locally concentrated ionic liquid electrolytes (LCILEs), exhibiting lower viscosity, faster Li+ transport, and enhanced compatibility toward lithium metal anodes, are feasible options for the next-generation high-energy-density LMBs. Herein, the progress of the recently developed LCILEs are summarised, including their physicochemical properties, solution structures, and applications in LMBs with a variety of high-energy cathode materials. Lastly, a perspective on the future research directions of LCILEs to further understanding and achieve improved cell performances is outlined.

Automated summary

Non-flammable ionic liquid electrolytes (ILEs) are potential candidates for safer and longer-lasting lithium metal batteries (LMBs), but their high viscosity and inadequate Li+ transport restrict their practical use. Recently, diluting ILEs with non-solvating and low-viscosity co-solvents has been employed to overcome these challenges. The resulting locally concentrated ionic liquid electrolytes (LCILEs) exhibit lower viscosity, faster Li+ transport, and improved compatibility with lithium metal anodes, making them promising options for next-generation high-energy-density LMBs. This article provides a summary of the progress made in the development of LCILEs, including their physicochemical properties, solution structures, and applications in LMBs with various high-energy cathode materials. Furthermore, future research directions for LCILEs are outlined to enhance our understanding and achieve better cell performance.