Solvent-Free, Single Lithium-Ion Conducting Covalent Organic Frameworks

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Porous crystalline materials like covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) are explored for ion conduction.
• Existing materials often require lithium salts and solvents, hindering true solid-state single-ion conduction.

Purpose of the Study:

• To introduce a novel solvent-free, single lithium-ion conductor based on a functionalized covalent organic framework.
• To investigate the ion transport properties and potential applications of this new material in lithium metal batteries.

Main Methods:

• Synthesis of a lithium sulfonated covalent organic framework (TpPa-SO₃Li).
• Characterization of its porous structure and ion-conducting properties.
• Electrochemical testing, including lithium plating/stripping on lithium metal electrodes.

Main Results:

• TpPa-SO₃Li achieved an ionic conductivity of 2.7 × 10^-5 S cm^-1.
• A high lithium-ion transference number of 0.9 was recorded at room temperature.
• The material demonstrated reversible and stable lithium plating/stripping without added salts or solvents.

Conclusions:

• TpPa-SO₃Li represents a new class of solvent-free, single lithium-ion conductors.
• Its unique ion transport characteristics are attributed to directional channels, high ion density, and tethered anions.
• The material shows significant potential for use in advanced lithium metal electrodes and batteries.