Ultralow-Temperature Carboxylate Electrolyte for High-Voltage Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Carbonate electrolytes in lithium metal batteries (LMBs) face challenges at cryogenic temperatures, including poor kinetics and interfacial instability.
• Carboxylate electrolytes offer lower viscosity but suffer from low oxidative stability and film formation.

Purpose of the Study:

• To design an ultralow-temperature electrolyte for high-voltage LMBs.
• To improve ion transfer kinetics and oxidative stability at cryogenic conditions.

Main Methods:

• Formulated an electrolyte using gamma-butyrolactone (GBL) and isobutyronitrile (iBN).
• Incorporated lithium nitrate (LiNO3) as an additive.
• Tested Li||LiNi0.8Co0.1Mn0.1O2 cells at temperatures ranging from -60°C to -20°C and a 4.5V cutoff voltage.

Main Results:

• The GBL/iBN electrolyte demonstrated enhanced Li+ ion transfer and oxidation stability.
• Dense, ionically conductive interfacial films were formed between -60°C and -20°C.
• A Li||LiNi0.8Co0.1Mn0.1O2 cell achieved 88.8 mAh g-1 capacity with 77.2% retention after 450 cycles at -40°C and 4.5V.
• At -50°C, the cell delivered 89.7 mAh g-1 with 99% retention over 50 cycles.

Conclusions:

• Combining carboxylate and nitrile solvents offers a promising strategy for ultralow-temperature LMB electrolytes.
• The developed electrolyte shows superior performance and interfacial stability in extreme cold conditions.
• This work provides insights for designing advanced electrolytes for demanding low-temperature applications.