Ring-chain synergy in ionic liquid electrolytes for lithium batteries.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Ionic liquids are promising electrolytes for lithium-ion batteries, addressing limitations of traditional electrolytes like flammability and high operating temperatures.
• However, ionic liquids face challenges at low temperatures, including poor ionic conductivity and phase transitions, hindering their widespread adoption.

Purpose of the Study:

• To develop and characterize a novel mixed electrolyte system for lithium-ion batteries.
• To enhance low-temperature performance, safety, and electrochemical stability of lithium-ion battery electrolytes.

Main Methods:

• Formulation of mixed electrolytes using N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (Pyr1,2O1TFSI) ionic liquid and lithium difluoro(oxalate)borate (LiODFB) lithium salt.
• Incorporation of cosolvents: ethylene sulfite (ES) or dimethyl sulfite (DMS).
• Evaluation of ion transport properties, electrochemical window, thermal stability, and electrode compatibility.

Main Results:

• The mixed electrolyte system demonstrated excellent ion transport with a conductivity of 8.163 mS cm⁻¹.
• Achieved a wide electrochemical window of 5.2 V and non-flammability.
• Exhibited a broad operating temperature range (-40 °C to 60 °C) and effective anode protection film formation.

Conclusions:

• The developed mixed electrolyte system, leveraging ring-chain synergy, significantly improves safety, ion transport, and electrode compatibility.
• This formulation overcomes the low-temperature limitations of traditional ionic liquid electrolytes, paving the way for advanced lithium-ion batteries.