Opportunity for eutectic mixtures in metal-ion batteries

Breakthroughs in super-concentrated electrolytes have pushed the aqueous solution to the forefront of the high-safety battery devices. An ideal electrolyte system should be cost-effective and stable in a wide electrochemical window. In recent years, eutectic mixtures have emerged as a green, safe, low-cost, and electrochemically stable electrolyte system for rechargeable metal-ion batteries (MIBs). Here, the fundamental understanding of the formation mechanisms, physio-chemical properties, and composition–structure–property relationships of eutectic mixtures are summarized. Our focus is their advanced function and applications in MIBs. Considering that eutectic mixtures in MIBs are still at an early stage, we provide the challenges and perspectives which hopefully may guide the rational design of advanced eutectic mixtures for different electrochemical energy storage and conversion systems.