Fast secondary dynamics for enhanced charge transport in polymerized ionic liquids

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Segmental dynamics in polymerized ionic liquids (PILs) are key to their ionic conductivity.
• PILs are promising electrolytes for energy storage devices like fuel cells and batteries.
• Existing models often overlook secondary relaxation modes' impact on charge transport.

Purpose of the Study:

• To investigate the influence of relaxation modes beyond segmental dynamics on ionic conductivity in PILs.
• To identify and characterize secondary relaxation processes in ionene-based PILs.
• To elucidate the molecular mechanisms governing enhanced ionic transport in PILs.

Main Methods:

• Dielectric spectroscopy was employed to study ionene-based PILs.
• Measurements were conducted across a range of temperatures and pressures (T-P thermodynamic space).
• Analysis focused on identifying and characterizing distinct relaxation processes.

Main Results:

• Dielectric studies revealed secondary relaxation modes that significantly impact ionic conductivity.
• A specific secondary relaxation (β process) was identified, enhancing segmental dynamics and ionic conductivity.
• This β process was experimentally confirmed to be Johari-Goldstein relaxation.
• The findings demonstrate that the studied PIL exhibits superionic properties due to coupled dynamics.

Conclusions:

• Secondary relaxation modes, particularly Johari-Goldstein relaxation, play a critical role in ionic conductivity of PILs.
• The identified β process enhances segmental dynamics, leading to superionic conductivity.
• These findings suggest a universal mechanism for fast ion transport in PILs, broadening their potential applications.