Coordination Regulation Enabling Deep Eutectic Electrolyte for Fast-Charging High-Voltage Lithium Metal Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium metal batteries (LMBs) require advanced electrolytes for high-voltage and fast-charging applications.
• Current electrolytes face challenges in safety and cycle stability under demanding conditions.

Purpose of the Study:

• To develop a novel sulfonate-based deep eutectic electrolyte (DEE) for improved LMB performance.
• To investigate the intermolecular coordination effects governing the DEE's electrochemical properties.

Main Methods:

• Synthesis of a DEE from sultone and lithium bis(trifluoromethanesulfonyl)imide.
• Nuclear magnetic resonance (NMR) spectroscopy to study intermolecular coordination.
• Electrochemical testing of LiFePO4||Li, LiNi0.88Co0.07Mn0.05O2||Li, and other high-voltage LMBs.
• Pouch cell fabrication to demonstrate practical applicability.

Main Results:

• The DEE exhibits controlled Li+ transport due to Li-O and F-H coordination, enabling 10 C fast charging with 95.1% capacity retention after 500 cycles in LiFePO4||Li cells.
• The electrolyte demonstrates an enhanced electrochemical stability window, facilitating stable cycling of high-voltage cathodes at 4.5 V (81.0% retention after 500 cycles in LiNi0.88Co0.07Mn0.05O2||Li cells).
• Excellent compatibility was observed with various high-voltage cathode materials (LiCoO2 and Li1.13Mn0.517Ni0.256Co0.097O2) and successful pouch cell implementation.

Conclusions:

• The designed DEE offers superior safety and cycle stability for demanding LMB applications.
• Intermolecular coordination is key to tailoring electrolyte properties for fast charging and high-voltage stability.
• This DEE represents a promising advancement for practical, high-performance lithium metal batteries.