Frozen organic electrolyte conducts lithium ions

What the study found: Frozen organic ice electrolytes can act as molecular-solid Li+ conductors for lithium metal batteries, challenging the idea that frozen electrolytes do not conduct ions. The authors report that a room-temperature ice-phase electrolyte, EC0.2T, showed high ionic conductivity and a high Li+ transference number.
Why the authors say this matters: The study suggests that frozen organic electrolytes may be useful for lithium metal batteries because they can conduct lithium ions in solid form. The findings indicate that EC0.2T also formed a solvent-derived, Li2O-rich solid electrolyte interphase, which the authors link to longer cycle life.
What the researchers tested: The researchers examined ethylene carbonate, a cyclic carbonate, and a specific formulation, EC0.2T, defined as 0.2 m LiTFSI in ethylene carbonate. They evaluated its frozen-state ion transport behavior and its performance in LFP||Li cells, where LFP stands for lithium iron phosphate.
What worked and what didn't: EC0.2T was reported to have ionic conductivity of about 0.64 mS cm^-1 and a Li+ transference number of about 0.8, with ion movement occurring by hopping through a solid matrix formed by immobilized solvent molecules. In LFP||Li cells, frozen EC0.2T delivered capacity at a level comparable to liquid electrolytes and extended cycle life; the abstract does not describe any specific failures.
What to keep in mind: The summary does not provide detailed experimental conditions beyond the stated formulation and cell type. It also does not describe limitations, side effects, or whether the results generalize beyond EC0.2T and the tested battery setup.

Key points

• Frozen organic electrolytes were reported to conduct Li+ ions rather than remain nonconductive.
• EC0.2T, defined as 0.2 m LiTFSI in ethylene carbonate, showed about 0.64 mS cm^-1 ionic conductivity.
• EC0.2T had a Li+ transference number of about 0.8.
• The study describes ion transport as hopping through a solid matrix of immobilized solvent molecules.
• Frozen EC0.2T delivered liquid-electrolyte-level capacity in LFP||Li cells and extended cycle life.