Perspective on eutectic electrolytes for next-generation batteries

The environmental challenges and growing energy demand have promoted the development of renewable energy, including solar, tidal, and wind. The next-generation electrochemical energy storage (EES), incorporating flow battery (FB) and metal-based battery (MB, Li, Na, Zn, Mg, etc.) received more attention. The flammable electrolytes in nonaqueous batteries have raised serious safety hazards and more unconventional electrolyte systems have been proposed recently. An emerging class of electrolytes, eutectic electrolytes have been reported in many batteries due to the facile preparation, concentrated states, and unique ion transport properties. In FB, eutectic electrolytes can significantly increase the energy density by promoting the molar ratio of redox active materials. In MB, eutectic electrolytes reduce the vapor pressure and toxicity, inhibit metal dendrites growth, and enlarge the electrochemical window. In this review, we summarize the progress status of different eutectic electrolytes on both FBs and MBs. We expect this review can supply the guidance for the application of eutectic electrolytes in EES.