Lithium Ion-Conducting Triazacoronene-Based Neutral 2D Covalent Organic Framework as a Solid-State Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Traditional liquid electrolytes in lithium-ion batteries (LIBs) pose safety risks and limit lifespan.
• Polymer electrolytes struggle with ionic conductivity and dendrite prevention, while inorganic electrolytes have poor processability.
• Crystalline, porous covalent organic frameworks (COFs) present a promising alternative for solid-state electrolytes (SSEs).

Purpose of the Study:

• To develop and characterize a new neutral 2D COF material for use as a solid-state electrolyte in LIBs.
• To evaluate the ionic conductivity, Li+ transference number, and electrochemical performance of the novel COF.

Main Methods:

• Synthesis of a neutral hexagonal 2D COF (HMTAC-COF1) using a heteroatom-rich hexamethoxy-triazacoronene (HMTAC) building block.
• Li+-doping of HMTAC-COF1 to create a solid-state electrolyte.
• Electrochemical testing of the SSE in a Li || Li+@HMTAC-COF1 || LiFePO4 coin cell.

Main Results:

• HMTAC-COF1 exhibited impressive ionic conductivity (4.95 × 10-5 S/cm at 20°C, 1.95 × 10-4 S/cm at 120°C) and low activation energy (0.25 eV).
• The SSE demonstrated a high Li+ transference number (0.57).
• The coin cell achieved a specific capacity of 181 mAh/g with over 99% Coulombic efficiency across multiple cycles.

Conclusions:

• Heteroatom-rich neutral COFs, like HMTAC-COF1, are viable candidates for advanced solid-state electrolytes.
• The developed COF material shows potential for enhancing the safety and performance of next-generation lithium-ion batteries.