Recent Advances in New-Generation Electrolytes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are one of the recent trends in energy storage systems due to their promising properties, the high abundance of sodium in the Earth's crust, and their low cost. However, the commercialization process of SIBs is in the early stages of development because of some challenges related to electrodes and electrolytes. Electrolytes are vital components of secondary batteries because they determine anode/cathode performance; energy density; operating conditions (electrochemical stability window, open circuit voltage, current rate, etc.); cyclic properties; electrochemical, thermal, mechanical, and dimensional stability; safety level; and the service life of the system. The performance of the battery is based on the structural, morphological, electrical, and electrochemical properties of the electrolytes. In this review, electrolytes used for SIBs are classified according to their state and material, including liquid, quasi-solid, solid, and hybrid, and recent advances in electrolyte research have been presented by considering their contributions and limitations. Additionally, future trends and recent cutting-edge research are highlighted.