Fluoride-ion-conducting Polymers: Ionic Conductivity and Fluoride Ion Diffusion Coefficient in Quaternized...

Area of Science:

• Polymer Chemistry
• Materials Science
• Electrochemistry

Background:

• Polysulfone (PSU) is a versatile aromatic polymer.
• Development of efficient polymeric fluoride ion conductors is crucial for advanced energy storage devices.

Purpose of the Study:

• To synthesize a novel polymeric fluoride ion conductor using polysulfone.
• To characterize the ionic conductivity and ion diffusion properties of the new material.

Main Methods:

• Three-step synthesis involving chloromethylation of PSU, quaternization with tertiary amines, and chloride-fluoride ion exchange.
• Measurement of fluoride ion conductivity using impedance spectroscopy.
• Determination of ion diffusion coefficients via pulsed gradient spin-echo (PGSE) NMR and impedance spectroscopy with the Nernst-Einstein relation.

Main Results:

• Achieved fluoride ion conductivity of 3-5 mS cm⁻¹ at 25°C and 5-10 mS cm⁻¹ at 40°C.
• Obtained diffusion coefficients in good agreement between PGSE NMR and impedance spectroscopy, ranging from 2 to 4×10⁻¹⁰ m² s⁻¹.
• Demonstrated the ability to estimate membrane porosity and tortuosity.

Conclusions:

• A novel, efficient polymeric fluoride ion conductor based on polysulfone has been successfully synthesized.
• The material exhibits competitive ionic conductivity and diffusion properties.
• The developed synthesis route offers a potentially less toxic alternative for producing advanced ionomers.