Ionic Liquid-Based Electrolytes for Aluminum/Magnesium/Sodium-Ion Batteries

Developing post-lithium-ion battery technology featured with high raw material abundance and low cost is extremely important for the large-scale energy storage applications, especially for the metal-based battery systems such as aluminum, sodium, and magnesium ion batteries. However, their developments are still in early stages, and one of the major challenges is to explore a safe and reliable electrolyte. An ionic liquid-based electrolyte is attractive and promising for developing safe and nonflammable devices with wide temperature ranges owing to their several unique properties such as ultralow volatility, high ionic conductivity, good thermal stability, low flammability, a wide electrochemical window, and tunable polarity and basicity/acidity. In this review, the recent emerging limitations and strategies of ionic liquid-based electrolytes in the above battery systems are summarized. In particular, for aluminum-ion batteries, the interfacial reaction between ionic liquid-based electrolytes and the electrode, the mechanism of aluminum storage, and the optimization of electrolyte composition are fully discussed. Moreover, the strategies to solve the problems of electrolyte corrosion and battery system side reactions are also highlighted. Finally, a general conclusion and a perspective focusing on the current development limitations and directions of ionic liquid-based electrolytes are proposed along with an outlook. In order to develop novel high-performance ionic liquid electrolytes, we need in-depth understanding and research on their fundamentals, paving the way for designing next-generation products.