Early Terminating Solid Electrolyte Interphase Formation via Nucleophilic Fluorination to Achieve High Initial...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Initial Coulombic efficiency (ICE) in lithium-ion batteries is limited by excessive solid electrolyte interphase (SEI) formation, reducing practical energy density.
• Current methods to improve SEI often consume lithium ions and offer limited gains.
• Targeting the SEI termination process presents a novel approach to enhance battery performance.

Purpose of the Study:

• To develop a strategy for early termination of SEI formation to achieve ICEs exceeding 90%.
• To investigate the mechanism of SEI termination using chemical fluorination on TiO2 electrodes.
• To demonstrate the practical applicability of the proposed method in pouch cells.

Main Methods:

• Equivalent chemical fluorination of TiO2 electrodes to suppress parasitic reactions.
• Interfacial analysis and theoretical simulations to understand SEI formation mechanisms.
• Electrochemical testing of pristine and fluorinated TiO2 anodes, including pouch cell tests.

Main Results:

• Chemical fluorination effectively suppressed parasitic reactions, leading to early SEI termination.
• Fluorinated TiO2 anodes achieved an ICE of 92.1%, a significant improvement over pristine TiO2 (74.1%).
• The method reduced organic SEI components while maintaining a beneficial LiF-rich inner SEI layer, without compromising other performance metrics.

Conclusions:

• Targeting the SEI termination process is a viable strategy for significantly enhancing initial Coulombic efficiency.
• Chemical fluorination offers a new pathway for inherent SEI manipulation and battery performance optimization.
• The demonstrated method shows practical applicability for improving lithium-ion battery energy density.