Electrolyte design for Li-ion batteries under extreme operating conditions

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Existing electrolytes for Lithium Nickel Manganese Cobalt Oxide (NMC811)||graphite batteries struggle to meet demands for high voltage, fast charging, wide temperature range, and safety.
• Electrolyte design is limited by a lack of guiding principles connecting battery performance, solvation structure, and solid-electrolyte-interphase (SEI) chemistry.

Purpose of the Study:

• To develop and validate a novel electrolyte design strategy for advanced lithium-ion batteries.
• To address the limitations of current electrolytes in achieving simultaneous high voltage, fast charging, wide temperature operation, and non-flammability.

Main Methods:

• A new electrolyte design strategy based on soft solvents was employed.
• The strategy focused on balancing Li+-solvent interactions, salt dissociation, and electrochemical properties.
• Performance was validated using NMC811||graphite coin and pouch cells under various temperature and charging conditions.

Main Results:

• The developed electrolyte enables 4.5-volt NMC811||graphite coin cells to retain significant capacity at -50°C (75%) and -60°C (54%) at 0.1C.
• NMC811||graphite pouch cells with lean electrolyte achieved stable cycling with >99.9% Coulombic efficiency at -30°C.
• Formation of similar lithium-fluoride-rich interphases on cathode and anode was observed, preventing lithium plating at low temperatures.

Conclusions:

• The soft solvent-based electrolyte design strategy successfully meets the requirements for high-voltage, fast-charging, wide-temperature, and safe lithium-ion batteries.
• This approach provides an effective guiding principle for future electrolyte development.
• The principle is potentially extendable to other alkali-metal-ion batteries for extreme condition applications.