Ester-Guided Dynamic Li⁺ Solvation Enables Plating-Less, Fast-Charging Li-Ion Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Extremely fast charging (XFC) is critical for electric vehicle (EV) adoption.
• Thick electrodes in EV cells hinder XFC with conventional electrolytes, causing lithium plating and inventory loss.
• Novel electrolyte formulations are needed to enable XFC in EV batteries.

Purpose of the Study:

• To develop and evaluate noncarbonate solvents for high-concentration electrolytes (HCEs) that enhance XFC capabilities.
• To investigate the performance of a methyl acetate (MA)-based HCE with an SEI-stabilizing additive (3MF) compared to a dimethyl carbonate (DMC) based HCE.
• To understand the underlying mechanisms of improved Li+ transport and interfacial kinetics.

Main Methods:

• Comparative analysis of MA-based and DMC-based HCEs.
• Investigation of solvation structures, interfacial kinetics, and bulk Li+ transport.
• Electrochemical testing of pouch cells with thick electrodes under various conditions, including low temperatures and high charge rates.

Main Results:

• The MA-based HCE with 3MF demonstrated superior XFC performance in a 1.2 Ah pouch cell.
• Outperformed DMC-based HCE in cycling stability at -20 °C and 10 C-rate (6-min charging).
• Showcased excellent performance with thick electrodes (6.0 mAh cm-2), mitigating Li plating.

Conclusions:

• MA-based HCEs satisfy energy barrier thresholds for Li+ desolvation and SEI migration.
• MA acts as a molecular lubricant, facilitating Li+ percolation pathways in HCEs.
• This approach is crucial for boosting XFC capabilities in next-generation EV batteries.