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

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, EC0.2T (0.2 m LiTFSI in ethylene carbonate), exhibited a high ionic conductivity (similar to 0.64 mS cm- 1) and a high Li+ transference number (similar to 0.8) via hopping mechanism through solid matrix formed by immobilized solvent molecules. Frozen EC0.2T 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.