Antisolvent-Regulated Anionic Coordination Enabling Stable Li Metal Anode in Urea-Based Electrolyte.

Area of Science:

• Electrochemistry
• Materials Science
• Battery Technology

Background:

• Stabilizing lithium metal batteries (LMBs) requires inorganic-rich solid electrolyte interphase (SEI) layers formed by nitrate (NO3-) anion solvation.
• Lithium nitrate (LiNO3) has limited solubility and challenging NO3- coordination due to its high donor number, hindering its application.

Purpose of the Study:

• To boost the cycling stability of LMBs by demonstrating an antisolvent-enhanced anionic coordination effect in urea-based LiNO3 electrolytes.
• To investigate the role of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) in modifying NO3- coordination within the solvation sheath.

Main Methods:

• Formulation of urea-based LiNO3 electrolytes with the addition of TTE.
• Analysis of solvation sheath structure and NO3- coordination using spectroscopic or computational methods (implied).
• Electrochemical testing of Li||Li, Li||Cu, and Li||LiFePO4 cells to evaluate cycling stability and Coulombic efficiency.

Main Results:

• TTE incorporation enhanced Li+-NO3- interactions and promoted ion-pair formation in the solvation sheath.
• NO3- anions transformed from monodentate to bidentate coordination, favoring preferential nitrate reduction at the anode.
• Optimized electrolytes achieved 6000 hours of operation in Li||Li cells and 99.6% Coulombic efficiency in Li||Cu cells.
• Li||LiFePO4 full cells retained 88% capacity after 100 cycles at 0.2C.

Conclusions:

• Antisolvent-enhanced anionic coordination is a viable strategy for improving SEI layers in LMBs.
• The TTE-modified urea-based electrolyte significantly enhances the electrochemical performance and stability of lithium metal anodes.
• This approach offers a promising pathway for developing high-performance and long-lasting lithium metal batteries.