Strong Solvent and Dual Lithium Salts Enable Fast-Charging Lithium-Ion Batteries Operating from -78 to 60 °C

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-ion batteries face performance limitations at high charge/discharge rates and low temperatures.
• Current carbonate electrolytes exhibit restricted Li+ conduction and slow Li+ desolvation, hindering battery efficiency under demanding conditions.

Purpose of the Study:

• To develop a novel electrolyte system that enhances lithium-ion battery performance across a wide temperature range and high current densities.
• To address the thermodynamic limitations of conventional electrolytes by molecular-level regulation of ion-solvent and ion-anion interactions.

Main Methods:

• Formulation of a dual lithium salt electrolyte using lithium bis(fluorosulfonyl)imide (LiFSI) and difluoro(oxalato)borate (DFOB-) in dimethyl sulfite (DMS) solvent.
• Characterization of electrolyte properties including Li+ conduction, desolvation, and electrode/electrolyte interface behavior.
• Performance testing of graphite||LiCoO2 pouch cells under various temperature conditions (-78 to 60 °C) and high current densities (up to 41.3 mA cm-2).

Main Results:

• The LiFSI/DFOB-/DMS electrolyte demonstrated rapid Li+ conduction and smooth Li+ desolvation over a wide temperature range.
• An ultrathin, self-limited electrode/electrolyte interface and electric double layer were formed, improving electrode compatibility.
• Stable cycling was achieved at high currents (41.3 mA cm-2) and temperatures from -78 to 60 °C.
• A 1 Ah pouch cell retained 80% capacity at -20 °C (2 C rate) and 86% at -50 °C (0.1 C rate).

Conclusions:

• The strong solvent and dual lithium salt strategy effectively overcomes thermodynamic limitations in electrolytes.
• This electrolyte design enables high-performance lithium-ion batteries capable of operating under extreme temperature and high-rate conditions.
• The findings provide a new pathway for developing advanced electrolytes for next-generation energy storage solutions.