Constructing Donor-Acceptor-Linked COFs Electrolytes to Regulate Electron Density and Accelerate the Li⁺ Migration in...

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Solid-state electrolytes are crucial for advanced lithium metal batteries.
• Controlling electronic density in electrolytes is key for selective ion transport.
• Donor-acceptor (D-A) systems offer a pathway to modulate electronic properties.

Purpose of the Study:

• To develop a high-performance solid-state electrolyte using D-A linked covalent organic frameworks (COFs).
• To investigate the role of intramolecular charge transfer and electronic density modulation in Li+ transport.
• To enhance the selectivity of Li+ migration and suppress lithium dendrite formation.

Main Methods:

• Synthesis of D-A linked COFs with a focus on F-based ligands.
• Characterization of the COF structure and electronic properties.
• Electrochemical testing of the solid-state electrolyte in Li metal symmetric and Li/LiFePO4 cells.

Main Results:

• The F-based ligand COF electrolyte demonstrated highly selective Li+ transference number (0.83).
• Achieved high ionic conductivity of 6.7 × 10-4 S cm-1 and excellent cyclic stability (1000 h).
• Superior performance in Li/LiFePO4 cells with 90.8% capacity retention after 300 cycles at 5C compared to C- and N-based ligands.

Conclusions:

• D-A linked COFs effectively modulate electronic density for enhanced Li+ kinetics.
• The strong D-A interaction between porphyrin donors and F-based acceptors accelerates Li+ conduction.
• This approach provides a new strategy for designing high-performance solid-state electrolytes for lithium metal batteries.