Lithium-Ion Conduction Through Frozen Phase of Organic Electrolytes for Lithium Batteries

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, Li₂O-rich solid electrolyte interphase.