Do Sol Cheong, Minjun Kwon, Pil‐Su Jung, Seongmin Yoo, Jinki Hong, Eun Seon Heo, Jeongin Lee, Yewon Choi, You‐Yeob Song, DH Seo, Hyun‐Kon Song
ABSTRACT Organic ice electrolytes in their frozen states are presented as molecular‐solid Li + conductors for lithium metal batteries (LMBs), challenging the notion that frozen electrolytes lack ionic conductivity. Ethylene carbonate, a cyclic carbonate, was predicted to form Li + ‐conductive channels in its frozen crystal structure. A room‐temperature ice‐phase electrolyte, EC 0.2T (0.2 m LiTFSI in ethylene carbonate), exhibited a high ionic conductivity (∼0.64 mS cm − 1 ) and a high Li + transference number (∼0.8) via hopping mechanism through solid matrix formed by immobilized solvent molecules. Frozen EC 0.2T delivered liquid‐electrolyte‐level capacity in LFP||Li cells and, more importantly, significantly extended cycle life with a solvent‐derived, Li 2 O‐rich solid electrolyte interphase.