Elucidating Kinetic-Mediated Polymerization Behavior for In Situ Formation of Fluorine-Containing Gel Polymer...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Fluorinated gel polymer electrolytes (FGPEs) are promising for lithium metal batteries (LMBs) due to stable solid electrolyte interphases (SEIs) and cathode compatibility.
• However, fluorine's electron-withdrawing nature slows polymerization, compromising FGPE mechanical properties and durability.

Purpose of the Study:

• To propose a design principle for in situ formation of fluorinated copolymers to regulate polymerization kinetics.
• To develop robust fluorinated-nitrogenated copolymer networks (FNPEs) for enhanced LMB performance.

Main Methods:

• In situ polymerization of trifluoroethyl methacrylate (TFEMA)-typed monomers with N-isopropylacrylamide (NIPAM).
• Crosslinking to form a copolymer network.
• Characterization of electrolyte properties and electrochemical performance in NCM811//Li full cells.
• Multiscale modeling investigations.

Main Results:

• Achieved uniform polymer chains with moderate molecular weights and a robust copolymer network.
• Demonstrated LiF-rich and Li3N-rich interphases.
• Exhibited high capacity retention (>80% over 225 cycles) in NCM811//Li full cells.
• Showcased wide operating temperature range (-15 to 60°C) and compatibility with pouch cell configurations.

Conclusions:

• Elucidated the kinetic challenges in in situ FGPE formation.
• Provided a new design principle for copolymer electrolytes for durable LMBs.
• FNPEs offer a viable pathway for advanced lithium metal battery applications.