Molecular Association Chemistry Enables High-Voltage Fast-Charging Lithium Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• High-voltage fast-charging lithium batteries (VFC-LBs) require electrolytes with a delicate balance of properties, including low solvation barriers, high ionic conductivity, and broad electrochemical stability.
• Single-solvent electrolytes struggle to meet these conflicting demands due to inherent correlations between energy levels and polarity.

Purpose of the Study:

• To develop a novel electrolyte strategy for VFC-LBs using molecular association chemistry.
• To achieve moderate polarity and a wide energy level in electrolyte solvents, crucial for VFC-LB performance.

Main Methods:

• Proposed a descriptor of molecular association energy, derived from non-bonding interactions, to screen suitable VFC solvents.
• Investigated an optimal fluorinated ethylene carbonate-ethyl acetate electrolyte composition.
• Conducted electrochemical performance tests on Li||NCM811 coin and pouch cells.

Main Results:

• The optimal electrolyte demonstrated stable cycling for Li||NCM811 cells at 4.7 V, retaining 68.4% capacity at 10C.
• 400 mAh Li||NCM811 pouch cells showed stable cycling between 2.8-4.7 V over 130 cycles.
• Molecular association chemistry induced aggregate solvation structures and suppressed NiO phase formation, enhancing VFC capability.

Conclusions:

• Molecular association chemistry is a viable strategy for designing electrolytes for VFC-LBs.
• This approach can be extended to other battery chemistries, including silicon@carbon||NCM811 and graphite||LiFePO4 batteries.
• The developed strategy offers a pathway to improved energy storage devices.