Remodeling Highly Fluorinated Electrolyte via Shielding Agent Regulation toward Practical Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Highly fluorinated electrolytes enhance lithium metal battery (LMB) electrochemical stability.
• Excessive fluorination reduces ionic conductivity and creates sluggish ion diffusion interphases.
• Need for strategies to balance fluorination benefits with conductivity limitations.

Purpose of the Study:

• To remodel Li+ solvation structure in highly fluorinated electrolytes using a shielding agent.
• To improve ionic conductivity and interphase properties in fluorinated electrolytes for LMBs.
• To enhance the electrochemical performance and cycle life of lithium metal batteries.

Main Methods:

• Introduction of fluorinated amide (FDMA) as a shielding agent in highly fluorinated electrolytes.
• Investigation of Li+ solvation structure modulation via FDMA's high donor number (DN).
• Electrochemical testing of Li||NCM622 and Li||NCM811 cells with optimized electrolytes.

Main Results:

• FDMA successfully remodeled Li+ solvation, interrupting Li+-dipole interactions and forming a stable solid-electrolyte interphase.
• The optimized FDMA/DFEC electrolyte exhibited high ionic conductivity and rapid Li+ desolvation.
• Li||NCM622 achieved 2000 cycles with 84.7% capacity retention; Li||NCM811 pouch cells exceeded 150 cycles.

Conclusions:

• The 'shielding' strategy effectively modulates solvation structure in highly fluorinated electrolytes.
• This approach overcomes limitations of excessive fluorination, enhancing LMB performance.
• The developed strategy offers a pathway for practical, high-performance lithium metal batteries.