Fundamentals and Applications of Eutectic Gel Electrolytes for Next-Generation Batteries

Eutectic gel electrolytes (EGEs), formed by incorporating deep eutectic solvents (DESs) into polymer matrices, represent a promising category of gel electrolytes for next-generation batteries. By combining the high ionic conductivity and tunable solvation environment of DESs with the mechanical robustness and structural integrity of polymer matrices, EGEs present an advantageous combination of electrochemical capability and structural reliability. This review provides a comprehensive overview of recent progress in the design, synthesis, and functional understanding of EGEs. Particular attention is given to the modulation of solvation structures, enhancement of electrode/electrolyte interfacial compatibility, and environmental adaptability. Major fabrication approaches, encompassing both in situ and ex situ methods, are comparatively evaluated with respect to their impact on electrochemical stability range, ionic transport characteristics, and mechanical durability. The integration of EGEs into next-generation batteries, such as lithium, sodium, zinc, and emerging multivalent magnesium systems, is critically examined, with emphasis on their roles in suppressing dendrite formation, enhancing electrolyte stability, and improving compatibility with reactive metal anodes. Finally, we outline current limitations and suggest future directions, emphasizing the need for deeper mechanistic insights into ion coordination and interface dynamics, along with scalable fabrication routes that can accelerate the deployment of EGEs in next-generation batteries combining high performance, flexibility, and inherent safety.