Quasi-Solid Electrolytes with Flexible Branches and Rigid Skeletons for High-Temperature Li Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Quasi-solid electrolytes (QSEs) are crucial for next-generation high-energy-density lithium metal batteries.
• High operating temperatures cause side reactions, limiting QSE performance, especially with high-voltage cathodes.

Purpose of the Study:

• To develop a nonflammable QSE with enhanced high-temperature stability and safety.
• To improve the electrochemical performance and interface stability of lithium metal batteries.

Main Methods:

• Fabrication of a QSE using in situ copolymerization with a dual-component polymer host.
• Incorporation of fire-retardant fluorine- and phosphorus-based plasticizers.
• Electrochemical testing of the QSE with LiFePO4 and LiCoO2 cathodes at elevated temperatures.

Main Results:

• The QSE exhibits a copolymer host with flexible branches for ion migration and a rigid skeleton for thermal stability.
• Optimized plasticizers effectively scavenge radicals, providing a wide electrochemical window (4.7 V) and excellent interface stability.
• Demonstrated high capacity retention (82.3% after 1000 cycles at 5 C, 80 °C) for LiFePO4 and stable cycling (400 cycles at 4.5 V, 60 °C) for LiCoO2.

Conclusions:

• The developed nonflammable QSE offers superior high-temperature performance and safety for lithium metal batteries.
• The QSE's unique structure and composition enable reversible lithium plating/stripping and compatibility with high-voltage cathodes.