Tailoring Electrolyte Solvation for LiF-Rich Solid Electrolyte Interphase toward a Stable Li Anode

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• High-performance lithium metal batteries require a solid electrolyte interphase (SEI) with mechanical strength and ionic conductivity to prevent lithium dendrite growth.
• Directly forming such an ideal SEI from conventional electrolytes remains a significant challenge in battery research.

Purpose of the Study:

• To develop a modified ionic liquid electrolyte (M-ILE) using a crowding diluent for constructing a superior SEI.
• To investigate the mechanism by which the diluent promotes SEI formation and enhances battery performance.

Main Methods:

• Utilized simulations and experimental validation to study the M-ILE.
• Incorporated 1,2-difluorobenzene (1,2-dfBen) as a crowding diluent in the ionic liquid electrolyte.
• Fabricated and tested Li/LiFePO4 and Li/LiNi0.5Co0.2Mn0.3O2 battery cells using the M-ILE.

Main Results:

• The 1,2-dfBen diluent induced a crowded electrolyte environment, promoting Li+-FSI- interactions and aggregate ion pair formation.
• The diluent actively participated in the reduction process, forming a robust SEI with high ionic conductivity.
• Li/LiFePO4 cells demonstrated 96% capacity retention over 250 cycles; Li/LiNi0.5Co0.2Mn0.3O2 cells retained 88% capacity after 100 cycles.

Conclusions:

• The crowding diluent strategy is effective for creating advanced SEIs in lithium metal batteries.
• This approach offers a promising pathway for improving the safety and cycle life of lithium metal batteries.
• The developed M-ILE significantly enhances the performance of lithium metal anodes by optimizing SEI properties.